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823100.9864The evolutionary atavistic endotoxin and neoplastic growth. A hypothesis on the potential role of atavistic endotoxin in carcinogenesis is proposed. The presence of an antigen identical to the endotoxin of gram-negative bacteria in tumour cells is confirmed by IgM class natural specific antibodies to endotoxin (IgMNAE) in rats by immunizing them with rat tumour tissue extracts. Rat normal tissue extracts do not increase the endogenous level of natural immunity to endotoxin, indicating the absence of a foreign antigen such as endotoxin in normal cells which are naturally devoid also of other parasitic features such as invasiveness and metastases, whereas tumour cells, during a prolonged latent period of carcinogenesis, acquire resistance to harmful factors, lose most of their genetic, antigenic, morphological and biochemical properties and become parasitic so as to survive in unfavourable conditions. With the regression of the mentioned properties of cells to the atavistic parasitic state, the synthesis of dormant endotoxin is activated together with an enhanced expression of evolutionary resistance-related genes and oncogenes. Atavistic endotoxin, produced and secreted by proliferating tumour cells, should cause chronic cachexia and septic states in cancer patients, similarly as in cases of endotoxemic septic shock where the endotoxin of gram-negative bacteria is the main pathogenic factor. Thus, the implications of the hypothesis indicate the diagnostic as well as prognostic and preventive significance of evolutionary atavistic endotoxin and also of endotoxin from gram-negative bacteria in human cancers. Natural specific antibodies to endotoxin can be helpful in creating new immunotherapeutic methods.201120943325
999610.9863In Situ Localization of Staphylococcus shinii and Staphylococcus succinus in Infected Rhipicephalus microplus Ticks: Implications for Biocontrol Strategies. Rhipicephalus microplus is a blood-sucking parasite that causes heavy infestations on cattle and is a vector for severe tick-borne diseases, such as anaplasmosis and babesiosis, and poses a significant threat to the cattle industry. Cattle ticks show increasing acaricide resistance, which creates an additional problem concerning the inefficient chemical control of tick populations in cattle-grazing areas, necessitating the exploration of alternative tick biocontrol methods. Our study aimed to demonstrate the acaropathogenic efficacy of two bacterial species during experimental infections on R. microplus. Our experimental data confirmed that S. shinii and S. succinus exhibited significant acaropathogenic properties against R. microplus, as demonstrated by the tracking of fluorescent-labeled bacteria within the engorged-tick body. Our experiments revealed that both bacterial species could infect the hemolymph, salivary glands, and vestibular vagina of the tick, inducing histological changes in the affected organs that may impair feeding as well as reproductive capabilities. Gené's organ infection was detected only in S. succinus. Our findings offer valuable insights for developing biocontrol strategies to manage Rhipicephalus microplus populations effectively.202439770285
873120.9858Isolation of Potato Endophytes and Screening of Chaetomium globosum Antimicrobial Genes. Antimicrobial peptides (AMPs) have natural antibacterial activities that pathogens find difficult to overcome. As a result of this occurrence, AMPs can act as an important substitute against the microbial resistance. In this study, we used plate confrontation tests to screen out 20 potential endophytes from potato tubers. Among them, endophyte F5 was found to significantly inhibit the growth of five different pathogenic fungi. Following that, phylogenetic analysis revealed that the internal transcribed spacer (ITS) sequences were 99% identical to Chaetomium globosum corresponding sequences. Thereafter, the Bacillus subtilis expression system was used to create a C. globosum cDNA library in order to isolate the resistance genes. Using this approach, the resistance gene screening technology in the indicator bacteria built-in library was used to identify two antimicrobial peptides, CgR2150 and CgR3101, with broad-spectrum antibacterial activities. Furthermore, the results showed that CgR2150 and CgR3101 have excellent UV, thermal, and enzyme stabilities. Also, these two peptides can significantly inhibit the growth of various bacteria (Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola, Clavibacter michiganensis, and Clavibacter fangii) and fungi (Fusarium graminearum, Rhizoctonia solani, and Botrytis cinerea). Scanning electron microscopy (SEM) observations revealed that CgR2150 and CgR3101 peptides act against bacteria by disrupting bacterial cell membranes. Moreover, hemolytic activity assay showed that neither of the two peptides exhibited significant hemolytic activity. To conclude, the antimicrobial peptides CgR2150 and CgR3101 are promising in the development of a new antibacterial agent and for application in plant production.202235563004
829530.9854Calcium Prevents Biofilm Dispersion in Bacillus subtilis. Biofilm dispersion is the final stage of biofilm development, during which biofilm cells actively escape from biofilms in response to deteriorating conditions within the biofilm. Biofilm dispersion allows cells to spread to new locations and form new biofilms in better locations. However, dispersal mechanisms have been elucidated only in a limited number of bacteria. Here, we investigated biofilm dispersion in Bacillus subtilis. Biofilm dispersion was clearly observed when B. subtilis was grown under static conditions in modified LB medium containing glycerol and manganese. Biofilm dispersion was synergistically caused by two mechanisms: decreased expression of the epsA operon encoding exopolysaccharide synthetases and the induction of sporulation. Indeed, constitutive expression of the epsA operon in the sporulation-defective ΔsigK mutant prevented biofilm dispersion. The addition of calcium to the medium prevented biofilm dispersion without significantly affecting the expression of the epsA operon and sporulation genes. In synthetic medium, eliminating calcium did not prevent the expression of biofilm matrix genes and, thereby, biofilm formation, but it attenuated biofilm architecture. These results indicate that calcium structurally stabilizes biofilms and causes resistance to biofilm dispersion mechanisms. Sporulation-dependent biofilm dispersion required the spoVF operon, encoding dipicolinic acid (DPA) synthase. During sporulation, an enormous amount of DPA is synthesized and stored in spores as a chelate with calcium. We speculate that, during sporulation, calcium bound to biofilm matrix components may be transported to spores as a calcium-DPA complex, which weakens biofilm structure and leads to biofilm dispersion. IMPORTANCE Bacteria growing as biofilms are notoriously difficult to eradicate and sometimes pose serious threats to public health. Bacteria escape from biofilms by degrading them when biofilm conditions deteriorate. This process, called biofilm dispersion, has been studied as a promising strategy for safely controlling biofilms. However, the regulation and mechanism of biofilm dispersion has been elucidated only in a limited number of bacteria. Here, we identified two biofilm dispersion mechanisms in the Gram-positive, spore-forming bacterium Bacillus subtilis. The addition of calcium to the medium stabilized biofilms and caused resistance to dispersal mechanisms. Our findings provide new insights into biofilm dispersion and biofilm control.202133927049
24040.9854Resistance of rumen bacteria murein to bovine gastric lysozyme. BACKGROUND: Lysozymes, enzymes mostly associated with defence against bacterial infections, are mureinolytic. Ruminants have evolved a gastric c type lysozyme as a digestive enzyme, and profit from digestion of foregut bacteria, after most dietary components, including protein, have been fermented in the rumen. In this work we characterized the biological activities of bovine gastric secretions against membranes, purified murein and bacteria. RESULTS: Bovine gastric extract (BGE) was active against both G+ and G- bacteria, but the effect against Gram- bacteria was not due to the lysozyme, since purified BGL had only activity against Gram+ bacteria. We were unable to find small pore forming peptides in the BGE, and found that the inhibition of Gram negative bacteria by BGE was due to an artefact caused by acetate. We report for first time the activity of bovine gastric lysozyme (BG lysozyme) against pure bacterial cultures, and the specific resistance of some rumen Gram positive strains to BGL. CONCLUSIONS: Some Gram+ rumen bacteria showed resistance to abomasum lysozyme. We discuss the implications of this finding in the light of possible practical applications of such a stable antimicrobial peptide.200415137912
30550.9853Toolkit Development for Cyanogenic and Gold Biorecovery Chassis Chromobacterium violaceum. Chromobacterium violaceum has been of interest recently due to its cyanogenic ability and its potential role in environmental sustainability via the biorecovery of gold from electronic waste. However, as with many nonmodel bacteria, there are limited genetic tools to implement the use of this Gram-negative chassis in synthetic biology. We propose a system that involves assaying spontaneous antibiotic resistances and using broad host range vectors to develop episomal vectors for nonmodel Gram-negative bacteria. These developed vectors can subsequently be used to characterize inducible promoters for gene expressions and implementing CRISPRi to inhibit endogenous gene expression for further studies. Here, we developed the first episomal genetic toolkit for C. violaceum consisting of two origins of replication, three antibiotic resistance genes, and four inducible promoter systems. We examined the occurrences of spontaneous resistances of the bacterium to the chosen selection markers to prevent incidences of false positives. We also tested broad host range vectors from four different incompatibility groups and characterized four inducible promoter systems, which potentially can be applied in other Gram-negative nonmodel bacteria. CRISPRi was also implemented to inhibit violacein pigment production in C. violaceum. This systematic toolkit will aid future genetic circuitry building in this chassis and other nonmodel bacteria for synthetic biology and biotechnological applications.202032160465
65060.9853Lipoplexes to Deliver Oligonucleotides in Gram-Positive and Gram-Negative Bacteria: Towards Treatment of Blood Infections. Bacterial resistance to antibiotics threatens the ability to treat life-threatening bloodstream infections. Oligonucleotides (ONs) composed of nucleic acid mimics (NAMs) able to inhibit essential genes can become an alternative to traditional antibiotics, as long as they are safely transported in human serum upon intravenous administration and they are carried across the multilayered bacterial envelopes, impermeable to ONs. In this study, fusogenic liposomes were considered to transport the ONs and promote their internalization in clinically relevant bacteria. Locked nucleic acids and 2'-OMethyl RNA were evaluated as model NAMs and formulated into DOTAP-DOPE liposomes followed by post-PEGylation. Our data showed a complexation stability between the post-PEGylated liposomes and the ONs of over 82%, during 24 h in native human serum, as determined by fluorescence correlation spectroscopy. Quantification by a lipid-mixing assay showed that liposomes, with and without post-PEGylation, fused with all bacteria tested. Such fusion promoted the delivery of a fraction of the ONs into the bacterial cytosol, as observed by fluorescence in situ hybridization and bacterial fractionation. In short, we demonstrated for the first time that liposomes can safely transport ONs in human serum and intracellularly deliver them in both Gram-negative and -positive bacteria, which holds promise towards the treatment of bloodstream infections.202134210111
61470.9851Ehrlichia chaffeensis and Anaplasma phagocytophilum lack genes for lipid A biosynthesis and incorporate cholesterol for their survival. Ehrlichia chaffeensis and Anaplasma phagocytophilum are agents of human monocytic and granulocytic ehrlichioses, respectively. They are extremely sensitive to mechanical stress and are pleomorphic gram-negative bacteria. Membrane incorporation of cholesterol from the eukaryotic host is known to be essential for other fragile and pleomorphic bacteria and mycoplasmas that lack a cell wall. Thus, we tested whether cholesterol is required for E. chaffeensis and A. phagocytophilum. Using a freeze fracture technique and biochemical analysis, these bacteria were found to contain significant levels of membrane cholesterol. These bacteria lack genes for cholesterol biosynthesis or modification. However, host cell-free bacteria had the ability to take up directly exogenous cholesterol or NBD-cholesterol, a fluorescent cholesterol derivative. Treatment of the bacteria with cholesterol extraction reagent methyl-beta-cyclodextrin caused their ultrastructural changes. Furthermore, pretreatment of the bacteria with methyl-beta-cyclodextrin or NBD-cholesterol deprived these bacteria of the ability to infect leukocytes, thus killing these obligate intracellular bacteria. Analysis of E. chaffeensis and A. phagocytophilum genome sequences revealed that these bacteria lack all genes for the biosynthesis of lipid A and most genes for the biosynthesis of peptidoglycan, which confer structural strength to gram-negative bacteria. Taken together, these results suggest that human ehrlichiosis agents became cholesterol dependent due to the loss of these genes. As the first report of gram-negative bacteria incorporating cholesterol for survival, these findings offer insight into the unique nature of their parasitism and imply that cholesterol is important in the control of human ehrlichioses.200312933880
23780.9851CsbD, a Novel Group B Streptococcal Stress Response Factor That Contributes to Bacterial Resistance against Environmental Bile Salts. Group B Streptococcus (GBS) can cause many serious infections and result in severe symptoms depending on the infected organs. To survive and initiate infection from the gastrointestinal tract, GBS must resist physiochemical factors, such as bile salts, a potent antibacterial compound in the intestine. We found that GBS isolated from diverse sources all possess the capability to defend bile salts and permit survival. By constructing the GBS A909 transposon mutant library (A909(Tn)), we identified several candidate genes that might participate in the bile salt resistance of GBS. The rodA and csbD genes were validated as relevant to bile salt resistance. The rodA gene was anticipated to be related to peptidoglycan synthesis and influence the bile salt resistance of GBS by cell wall construction. Notably, we found that the csbD gene worked as a bile salt resistance response factor and influenced several ABC transporter genes, specifically at the later growth period of GBS under bile salt stress. We further detected the marked intracellular bile salt accumulation in ΔcsbD by hydrophilic interaction chromatography-liquid chromatography/mass spectrometry (HILIC-LC/MS). Collectively, we showed a novel GBS stress response factor, csbD, contributes to bacterial survival in bile salts by sensing bile salt stress and subsequently induces transcription of transporter genes to excrete bile salts. IMPORTANCE GBS, a conditional pathogenetic colonizer of the human intestinal flora, can cause severe infectious diseases in immunocompromised patients. Therefore, it is critical to understand the factors that contribute to the resistance to bile salts, which are abundant in the intestine but harmful to bacteria. We identified rodA and csbD genes involved in bile salt resistance using a transposon insertion site sequencing (TIS-seq) based screen. The rodA gene products might be involved in peptidoglycan synthesis as important contributors to stress resistance including bile salts. However, the csbD gene conferred bile salt resistance by promoting transporter genes transcription at the later growth period of GBS in response to bile salts. These findings developed a better understanding of the stress response factor csbD on the bile salt resistance of GBS.202337195202
1890.9851Antivirulence effects of cell-free culture supernatant of endophytic bacteria against grapevine crown gall agent, Agrobacterium tumefaciens, and induction of defense responses in plantlets via intact bacterial cells. BACKGROUND: Crown gall disease caused by Agrobacterium tumefaciens is a very destructive affliction that affects grapevines. Endophytic bacteria have been discovered to control plant diseases via the use of several mechanisms. This research examined the potential for controlling crown gall by three endophytic bacteria that were previously isolated from healthy cultivated and wild grapevines including Pseudomonas kilonensis Ba35, Pseudomonas chlororaphis Ba47, and Serratia liquefaciens Ou55. RESULT: At various degrees, three endophytic bacteria suppressed the populations of A. tumefaciens Gh1 and greatly decreased the symptoms of crown gall. Furthermore, biofilm production and motility behaviors of A. tumefaciens Gh1were greatly inhibited by the Cell-free Culture Supernatant (CFCS) of endophytic bacteria. According to our findings, CFCS may reduce the adhesion of A. tumefaciens Gh1 cells to grapevine cv. Rashe root tissues as well as their chemotaxis motility toward the extract of the roots. When compared to the untreated control, statistical analysis showed that CFCS significantly reduced the swimming, twitching, and swarming motility of A. tumefaciens Gh1. The findings demonstrated that the endophytic bacteria effectively stimulated the production of plant defensive enzymes including superoxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), and total soluble phenols at different time intervals in grapevine inoculated with A. tumefaciens Gh1. The Ba47 strain markedly increased the expression levels of defense genes associated with plant resistance. The up-regulation of PR1, PR2, VvACO1, and GAD1 genes in grapevine leaves indicates the activation of SA and JA pathways, which play a role in enhancing resistance to pathogen invasion. The results showed that treating grapevine with Ba47 increased antioxidant defense activities and defense-related gene expression, which reduced oxidative damage caused by A. tumefaciens and decreased the incidence of crown gall disease. CONCLUSION: This is the first study on how A. tumefaciens, the grapevine crown gall agent, is affected by CFCS generated by endophytic bacteria in terms of growth and virulence features. To create safer plant disease management techniques, knowledge of the biocontrol processes mediated by CFCS during microbial interactions is crucial.202438336608
9065100.9850Gut Bacteria Promote Phosphine Susceptibility of Tribolium castaneum by Aggravating Oxidative Stress and Fitness Costs. Knowledge about resistance mechanisms can provide ideas for pesticide resistance management. Although several studies have unveiled the positive or negative impacts of gut microbes on host pesticide resistance, minimal research is available regarding the association between gut microbes and host phosphine resistance. To explore the influence of gut bacteria on host phosphine susceptibility and its molecular basis, mortality, fitness, redox responses, and immune responses of adult Tribolium castaneum were determined when it was challenged by phosphine exposure and/or gut bacteria inoculation. Five cultivable gut bacteria were excised from a population of phosphine-resistant T. castaneum. Among them, only Enterococcus sp. inoculation significantly promoted host susceptibility to phosphine, while inoculation of any other gut bacteria had no significant effect on host phosphine susceptibility. Furthermore, when T. castaneum was exposed to phosphine, Enterococcus sp. inoculation decreased the female fecundity, promoted host oxidative stress, and suppressed the expression and activity of host superoxide dismutase, catalase, and peroxidase. In the absence of phosphine, Enterococcus sp. inoculation also elicited overactive immune responses in T. castaneum, including the immune deficiency and Toll signaling pathways and the dual oxidase-reactive oxygen species system. These results indicate that Enterococcus sp. likely promotes host phosphine susceptibility by aggravating oxidative stress and fitness costs.202337887827
8753110.9850Rhizosphere Bacteria From Panax notoginseng Against Meloidogyne hapla by Rapid Colonization and Mediated Resistance. Root-knot nematodes (RKNs) are soil-borne pathogens that severely affect Panax notoginseng growth and productivity. Thus, there is an urgent need for biological control agents or green nematicides to control root-knot nematodes. Rhizosphere bacteria can effectively control RKNs through different mechanisms. In this study, the three rhizosphere Bacillus strains, isolated from the root of P. notoginseng, were evaluated for the nematicidal activity and biological control efficacy against root-knot nematodes. In addition, we also evaluated the colonization ability of the two bacterial strains with significant biocontrol effect and dynamic regulation of genes related to systemic resistance in P. notoginseng. The rhizosphere Bacillus velezensis GJ-7 and Bacillus cereus NS-2 showed high nematicidal activity against Meloidogyne hapla in vitro and significantly reduced the number of root galls in three different control experiments. The results of colonization experiments showed that the strains GJ-7 and NS-2 colonized P. notoginseng root rapidly and stably. Additionally, the colonization of the strains NS-2 and GJ-7 activated the defense-responsive genes in P. notoginseng. These results indicated that the B. cereus strain NS-2 and B. velezensis strain GJ-7 have the potential for successful ecological niche occupation and enhance plant resistance and therefore could be considered as potential biocontrol agents against root-knot nematodes.202235572637
6018120.9849Effect of Trehalose and Lactose Treatments on the Freeze-Drying Resistance of Lactic Acid Bacteria in High-Density Culture. Freeze-drying is a commonly used method in commercial preparations of lactic acid bacteria. However, some bacteria are killed during the freeze-drying process. To overcome this, trehalose and lactose are often used as protective agents. Moreover, high-density culture is an efficient way to grow bacterial strains but creates a hypertonic growth environment. We evaluated the effects of trehalose and lactose, as a primary carbon source or as an additive in fermentation, on the freeze-drying survival of Lactobacillus fermentum FXJCJ6-1, Lactobacillus brevis 173-1-2, and Lactobacillus reuteri CCFM1040. Our results showed that L. fermentum FXJCJ6-1 accumulated but did not use intracellular trehalose in a hypertonic environment, which enhanced its freeze-drying resistance. Furthermore, genes that could transport trehalose were identified in this bacterium. In addition, both the lactose addition and lactose culture improved the freeze-drying survival of the bacterium. Further studies revealed that the added lactose might exert its protective effect by attaching to the cell surface, whereas lactose culture acted by reducing extracellular polysaccharide production and promoting the binding of the protectant to the cell membrane. The different mechanisms of lactose and trehalose in enhancing the freeze-drying resistance of bacteria identified in this study will help to elucidate the anti-freeze-drying mechanisms of other sugars in subsequent investigations.202236677339
8134130.9849Sweet scents from good bacteria: Case studies on bacterial volatile compounds for plant growth and immunity. Beneficial bacteria produce diverse chemical compounds that affect the behavior of other organisms including plants. Bacterial volatile compounds (BVCs) contribute to triggering plant immunity and promoting plant growth. Previous studies investigated changes in plant physiology caused by in vitro application of the identified volatile compounds or the BVC-emitting bacteria. This review collates new information on BVC-mediated plant-bacteria airborne interactions, addresses unresolved questions about the biological relevance of BVCs, and summarizes data on recently identified BVCs that improve plant growth or protection. Recent explorations of bacterial metabolic engineering to alter BVC production using heterologous or endogenous genes are introduced. Molecular genetic approaches can expand the BVC repertoire of beneficial bacteria to target additional beneficial effects, or simply boost the production level of naturally occurring BVCs. The effects of direct BVC application in soil are reviewed and evaluated for potential large-scale field and agricultural applications. Our review of recent BVC data indicates that BVCs have great potential to serve as effective biostimulants and bioprotectants even under open-field conditions.201626177913
6016140.9849Investigating human-derived lactic acid bacteria for alcohol resistance. BACKGROUND: Excessive alcohol consumption has been consistently linked to serious adverse health effects, particularly affecting the liver. One natural defense against the detrimental impacts of alcohol is provided by alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH), which detoxify harmful alcohol metabolites. Recent studies have shown that certain probiotic strains, notably Lactobacillus spp., possess alcohol resistance and can produce these critical enzymes. Incorporating these probiotics into alcoholic beverages represents a pioneering approach that can potentially mitigate the negative health effects of alcohol while meeting evolving consumer preferences for functional and health-centric products. RESULTS: Five lactic acid bacteria (LAB) isolates were identified: Lactobacillus paracasei Alc1, Lacticaseibacillus rhamnosus AA, Pediococcus acidilactici Alc3, Lactobacillus paracasei Alc4, and Pediococcus acidilactici Alc5. Assessment of their alcohol tolerance, safety, adhesion ability, and immunomodulatory effects identified L. rhamnosus AA as the most promising alcohol-tolerant probiotic strain. This strain also showed high production of ADH and ALDH. Whole genome sequencing analysis revealed that the L. rhamnosus AA genome contained both the adh (encoding for ADH) and the adhE (encoding for ALDH) genes. CONCLUSIONS: L. rhamnosus AA, a novel probiotic candidate, showed notable alcohol resistance and the capability to produce enzymes essential for alcohol metabolism. This strain is a highly promising candidate for integration into commercial alcoholic beverages upon completion of comprehensive safety and functionality evaluations.202438659044
8325150.9848The Effects of Airflow on the Mechanosensitive Channels of Escherichia coli MG1655 and the Impact of Survival Mechanisms Triggered. Understanding how bacteria respond to ventilated environments is a crucial concept, especially when considering accurate airflow modeling and detection limits. To properly design facilities for aseptic conditions, we must minimize the parameters for pathogenic bacteria to thrive. Identifying how pathogenic bacteria continue to survive, particularly due to their multi-drug resistance characteristics, is necessary for designing sterile environments and minimizing pathogen exposure. A conserved characteristic among bacterial organisms is their ability to maintain intracellular homeostasis for survival and growth in hostile environments. Mechanosensitive (MS) channels are one of the characteristics that guide this phenomenon. Interestingly, during extreme stress, bacteria will forgo favorable homeostasis to execute fast-acting survival strategies. Physiological sensors, such as MS channels, that trigger this survival mechanism are not clearly understood, leaving a gap in how bacteria translate physical stress to an intracellular response. In this paper, we study the role of mechanosensitive ion channels that are potentially triggered by aerosolization. We hypothesize that change in antimicrobial uptake is affected by aerosolization stress. Bacteria regulate their defense mechanisms against antimicrobials, which leads to varying susceptibility. Based on this information we hypothesize that aerosolization stress affects the antimicrobial resistance defense mechanisms of Escherichia coli (E. coli). We analyzed the culturability of knockout E. coli strains with different numbers of mechanosensitive channels and compared antibiotic susceptibility under stressed and unstressed airflow conditions. As a result of this study, we can identify how the defensive mechanisms of resistant bacteria are triggered for their survival in built environments. By changing ventilation airflow velocity and observing the change in antibiotic responses, we show how pathogenic bacteria respond to ventilated environments via mechanosensitive ion channels.202337764080
6020160.9847Safety evaluation of Lactococcus lactis IDCC 2301 isolated from homemade cheese. For applications of microorganisms as probiotics in the food industry, safety evaluation has increasingly become important to ensure the health of consumers. Although people have been using various lactic acid bacteria for different purposes, some studies have reported that certain lactic acid bacteria exhibit properties of virulence and produce toxic compounds. Thus, it is necessary to examine the characteristics associated with lactic acid bacteria that are safe for use as probiotics. This research aimed to assess the safety of Lactococcus lactis IDCC 2301 isolated from homemade cheese using in vitro and in vivo assays, including antibiotic resistance, hemolytic activity, toxin production, infectivity, and metabolic activity in immune-compromised animal species. The results demonstrated that the strain was susceptible to nine antibiotics suggested by the European Food Safety Authority (EFSA). Whole-genome analysis revealed that L. lactis IDCC 2301 neither has toxigenic genes nor harbors antibiotic resistance. Moreover, L. lactis IDCC 2301 showed neither hemolytic nor β-glucuronidase activity. Furthermore, none of the D-lactate and biogenic amines were produced by L. lactis IDCC 2301. Finally, it was demonstrated that there was no toxicity and mortality using single-dose oral toxicity tests in rats. These results indicate that L. lactis IDCC 2301 can be safely used as probiotics for human consumption.202235035910
9147170.9847A Critical Review on the Potential of Inactivated Bacteria in Counteracting Human Pathogens. Bacterial infections are a major global public health challenge, especially with increasing antibiotic resistance. Postbiotics, bioactive compounds produced by probiotics, have been proposed as a novel strategy to inhibit the growth of pathogenic bacteria and address antibiotic resistance. Similar to probiotics and certain food ingredients, postbiotics can also modulate beneficial microbial communities and ultimately contribute to host health. Postbiotics derived from probiotics may affect the physical and chemical conditions of the intestinal environment, and by enhancing the host's immune system, directly interfere with the metabolic pathways and signaling of pathogenic bacteria. Postbiotics inhibit biofilm formation, reduce the expression of antibiotic resistance genes, and enhance the efficacy of antibiotic therapies. They are effective against resistant bacteria such as Escherichia coli and Clostridium difficile and reduce the risk of dental infections caused by Streptococcus mutans. Some postbiotics, such as lactic acid and antimicrobial peptides derived from Lactobacillus and Bifidobacterium genus, help the immune system dealing resistant bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, and Helicobacter pylori. The review investigates the mechanisms of action and applications of postbiotics in the control of pathogenic bacteria and their role as a complement to existing treatments.202540394322
307180.9847Escape from Lethal Bacterial Competition through Coupled Activation of Antibiotic Resistance and a Mobilized Subpopulation. Bacteria have diverse mechanisms for competition that include biosynthesis of extracellular enzymes and antibiotic metabolites, as well as changes in community physiology, such as biofilm formation or motility. Considered collectively, networks of competitive functions for any organism determine success or failure in competition. How bacteria integrate different mechanisms to optimize competitive fitness is not well studied. Here we study a model competitive interaction between two soil bacteria: Bacillus subtilis and Streptomyces sp. Mg1 (S. Mg1). On an agar surface, colonies of B. subtilis suffer cellular lysis and progressive degradation caused by S. Mg1 cultured at a distance. We identify the lytic and degradative activity (LDA) as linearmycins, which are produced by S. Mg1 and are sufficient to cause lysis of B. subtilis. We obtained B. subtilis mutants spontaneously resistant to LDA (LDAR) that have visibly distinctive morphology and spread across the agar surface. Every LDAR mutant identified had a missense mutation in yfiJK, which encodes a previously uncharacterized two-component signaling system. We confirmed that gain-of-function alleles in yfiJK cause a combination of LDAR, changes in colony morphology, and motility. Downstream of yfiJK are the yfiLMN genes, which encode an ATP-binding cassette transporter. We show that yfiLMN genes are necessary for LDA resistance. The developmental phenotypes of LDAR mutants are genetically separable from LDA resistance, suggesting that the two competitive functions are distinct, but regulated by a single two-component system. Our findings suggest that a subpopulation of B. subtilis activate an array of defensive responses to counter lytic stress imposed by competition. Coordinated regulation of development and antibiotic resistance is a streamlined mechanism to promote competitive fitness of bacteria.201526647299
235190.9847Effect of Application of Probiotic Pollen Suspension on Immune Response and Gut Microbiota of Honey Bees (Apis mellifera). Although the use of probiotic bacteria in invertebrates is still rare, scientists have begun to look into their usage in honey bees. The probiotic preparation, based on the autochthonous strain Lactobacillus brevis B50 Biocenol™ (CCM 8618), which was isolated from the digestive tracts of healthy bees, was applied to the bee colonies in the form of a pollen suspension. Its influence on the immune response was determined by monitoring the expression of genes encoding immunologically important molecules in the honey bee intestines. Changes in the intestinal microbiota composition were also studied. The results showed that the probiotic Lact. brevis B50, on a pollen carrier, significantly increased the expression of genes encoding antimicrobial peptides (abaecin, defensin-1) as well as pattern recognition receptors (toll-like receptor, peptidoglycan recognition proteins). Gene expression for the other tested molecules included in Toll and Imd signaling pathways (dorsal, cactus, kenny, relish) significantly changed during the experiment. The positive effect on intestinal microbiota was manifested mainly by a significant increase in the ratio of lactic acid bacteria to enterobacteria. These findings confirm the potential of the tested probiotic preparation to enhance immunity in bee colonies and thus increase their resistance to infectious diseases and stress conditions.202031912341