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61400.9546Ehrlichia 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
55310.9529Single-cell analysis of glycopeptide resistance gene expression in teicoplanin-resistant mutants of a VanB-type Enterococcus faecalis. The vanB gene cluster confers resistance to vancomycin but not to the related antibiotic teicoplanin, as the VanRB SB two-component regulatory system triggers expression of the glycopeptide resistance genes only in response to vancomycin. The VanRB regulator activates promoters PRB and PYB for transcription of the regulatory (vanRB SB) and resistance (vanYB WHB BXB) genes respectively. The gfpmut1 gene encoding a green fluorescent protein was fused to PYB to analyse promoter activation in single cells by fluorescence microscopy and flow cytometry. Characterization of 17 teicoplanin-resistant mutants indicated that amino acid substitutions on either side of the VanSB autophosphorylation site led to a constitutive phenotype. Substitutions in the membrane-associated domain resulted in a gain of function, as they allowed induction by teicoplanin. A vanSB null mutant expressed gfpmut1 at various levels under non-inducing conditions, and the majority of the bacteria were not fluorescent. Bacteria grown in the presence of vancomycin or teicoplanin were homogeneously fluorescent. The increase in the number of fluorescent bacteria resulted from induction in negative cells rather than from selection of a resistant subpopulation, indicating that VanRB was activated by cross-talk. Transglycosylase inhibition was probably the stimulus for the heterologous kinase, as moenomycin was also an inducer.199910216856
33920.9528Multiple mechanisms of resistance to cisplatin toxicity in an Escherichia coli K12 mutant. The mechanisms underlying cellular resistance to the antitumor drug cis-diamminedichloro-platinum(II) (CDDP) were studied in Escherichia coli K12. A bacterial strain (MC4100/DDP) was selected from the MC4100 wild-type strain after growth for four cycles in CDDP. MC4100/DDP bacteria showed a high level of resistance and exhibited various modifications including (1) a decrease in drug uptake and platinum/DNA binding which only partly contributed to resistance, (2) an increase in glutathione content not involved in the resistant phenotype, (3) an increase in DNA repair capacity. Resistance was unmodified by introducing a uvrA mutation which neutralizes the excision-repair pathway. In contrast, it was abolished by deletion of the recA gene which abolishes recombination and SOS repair but also by a mutation in the recA gene leading to RecA co-protease minus (no SOS induction). RecA protein was unchanged in MC4100/DDP but the expression of RecA-dependent gene(s) was required for CDDP resistance. The regulation of genes belonging to the SOS regulon was analysed in MC4100/DDP by monitoring the expression of sfiA and recA::lacZ gene fusions after UV irradiation. These gene fusions were derepressed faster and the optimal expression was obtained for a lower number of UV lesions in MC4100/DDP, suggesting a role of RecA co-protease activity in the mechanism of resistance to CDDP in this E. coli strain.19947974517
818630.9526Tumor-infiltrating bacteria disrupt cancer epithelial cell interactions and induce cell-cycle arrest. Tumor-infiltrating bacteria are increasingly recognized as modulators of cancer progression and therapy resistance. We describe a mechanism by which extracellular intratumoral bacteria, including Fusobacterium, modulate cancer epithelial cell behavior. Spatial imaging and single-cell spatial transcriptomics show that these bacteria predominantly localize extracellularly within tumor microniches of colorectal and oral cancers, characterized by reduced cell density, transcriptional activity, and proliferation. In vitro, Fusobacterium nucleatum disrupts epithelial contacts, inducing G0-G1 arrest and transcriptional quiescence. This state confers 5-fluorouracil resistance and remodels the tumor microenvironment. Findings were validated by live-cell imaging, spatial profiling, mouse models, and a 52-patient colorectal cancer cohort. Transcriptomics reveals downregulation of cell cycle, transcription, and antigen presentation genes in bacteria-enriched regions, consistent with a quiescent, immune-evasive phenotype. In an independent rectal cancer cohort, high Fusobacterium burden correlates with reduced therapy response. These results link extracellular bacteria to cancer cell quiescence and chemoresistance, highlighting microbial-tumor interactions as therapeutic targets.202541106380
61640.9522Identification of lipoteichoic acid as a ligand for draper in the phagocytosis of Staphylococcus aureus by Drosophila hemocytes. Phagocytosis is central to cellular immunity against bacterial infections. As in mammals, both opsonin-dependent and -independent mechanisms of phagocytosis seemingly exist in Drosophila. Although candidate Drosophila receptors for phagocytosis have been reported, how they recognize bacteria, either directly or indirectly, remains to be elucidated. We searched for the Staphylococcus aureus genes required for phagocytosis by Drosophila hemocytes in a screening of mutant strains with defects in the structure of the cell wall. The genes identified included ltaS, which encodes an enzyme responsible for the synthesis of lipoteichoic acid. ltaS-dependent phagocytosis of S. aureus required the receptor Draper but not Eater or Nimrod C1, and Draper-lacking flies showed reduced resistance to a septic infection of S. aureus without a change in a humoral immune response. Finally, lipoteichoic acid bound to the extracellular region of Draper. We propose that lipoteichoic acid serves as a ligand for Draper in the phagocytosis of S. aureus by Drosophila hemocytes and that the phagocytic elimination of invading bacteria is required for flies to survive the infection.200919890048
906250.9520Biological cost of pyocin production during the SOS response in Pseudomonas aeruginosa. LexA and two structurally related regulators, PrtR and PA0906, coordinate the Pseudomonas aeruginosa SOS response. RecA-mediated autocleavage of LexA induces the expression of a protective set of genes that increase DNA damage repair and tolerance. In contrast, RecA-mediated autocleavage of PrtR induces antimicrobial pyocin production and a program that lyses cells to release the newly synthesized pyocin. Recently, PrtR-regulated genes were shown to sensitize P. aeruginosa to quinolones, antibiotics that elicit a strong SOS response. Here, we investigated the mechanisms by which PrtR-regulated genes determine antimicrobial resistance and genotoxic stress survival. We found that induction of PrtR-regulated genes lowers resistance to clinically important antibiotics and impairs the survival of bacteria exposed to one of several genotoxic agents. Two distinct mechanisms mediated these effects. Cell lysis genes that are induced following PrtR autocleavage reduced resistance to bactericidal levels of ciprofloxacin, and production of extracellular R2 pyocin was lethal to cells that initially survived UV light treatment. Although typically resistant to R2 pyocin, P. aeruginosa becomes transiently sensitive to R2 pyocin following UV light treatment, likely because of the strong downregulation of lipopolysaccharide synthesis genes that are required for resistance to R2 pyocin. Our results demonstrate that pyocin production during the P. aeruginosa SOS response carries both expected and unexpected costs.201425022851
10360.9517IL-1 receptor regulates S100A8/A9-dependent keratinocyte resistance to bacterial invasion. Previously, we reported that epithelial cells respond to exogenous interleukin (IL)-1α by increasing expression of several genes involved in the host response to microbes, including the antimicrobial protein complex calprotectin (S100A8/A9). Given that S100A8/A9 protects epithelial cells against invading bacteria, we studied whether IL-1α augments S100A8/A9-dependent resistance to bacterial invasion of oral keratinocytes. When inoculated with Listeria monocytogenes, human buccal epithelial (TR146) cells expressed and released IL-1α. Subsequently, IL-1α-containing media from Listeria-infected cells increased S100A8/A9 gene expression in naïve TR146 cells an IL-1 receptor (IL-1R)-dependent manner. Incubation with exogenous IL-1α decreased Listeria invasion into TR146 cells, whereas invasion increased with IL-1R antagonist. Conversely, when S100A8/A9 genes were knocked down using short hairpin RNA (shRNA), TR146 cells responded to exogenous IL-1α with increased intracellular bacteria. These data strongly suggest that infected epithelial cells release IL-1α to signal neighboring keratinocytes in a paracrine manner, promoting S100A8/A9-dependent resistance to invasive L. monocytogenes.201222031183
7770.9516A pathogen-inducible patatin-like lipid acyl hydrolase facilitates fungal and bacterial host colonization in Arabidopsis. Genes and proteins related to patatin, the major storage protein of potato tubers, have been identified in many plant species and shown to be induced by a variety of environmental stresses. The Arabidopsis patatin-like gene family (PLPs) comprises nine members, two of which (PLP2 and PLP7) are strongly induced in leaves challenged with fungal and bacterial pathogens. Here we show that accumulation of PLP2 protein in response to Botrytis cinerea or Pseudomonas syringae pv. tomato (avrRpt2) is dependent on jasmonic acid and ethylene signaling, but is not dependent on salicylic acid. Expression of a PLP2-green fluorescent protein (GFP) fusion protein and analysis of recombinant PLP2 indicates that PLP2 encodes a cytoplasmic lipid acyl hydrolase with wide substrate specificity. Transgenic plants with altered levels of PLP2 protein were generated and assayed for pathogen resistance. Plants silenced for PLP2 expression displayed enhanced resistance to B. cinerea, whereas plants overexpressing PLP2 were much more sensitive to this necrotrophic fungus. We also established a positive correlation between the level of PLP2 expression in transgenic plants and cell death or damage in response to paraquat treatment or infection by avirulent P. syringae. Interestingly, repression of PLP2 expression increased resistance to avirulent bacteria, while PLP2-overexpressing plants multiplied avirulent bacteria close to the titers reached by virulent bacteria. Collectively, the data indicate that PLP2-encoded lipolytic activity can be exploited by pathogens with different lifestyles to facilitate host colonization. In particular PLP2 potentiates plant cell death inflicted by Botrytis and reduces the efficiency of the hypersensitive response in restricting the multiplication of avirulent bacteria. Both effects are possibly mediated by providing fatty acid precursors of bioactive oxylipins.200516297072
54380.9515OxyR2 Modulates OxyR1 Activity and Vibrio cholerae Oxidative Stress Response. Bacteria have developed capacities to deal with different stresses and adapt to different environmental niches. The human pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, utilizes the transcriptional regulator OxyR to activate genes related to oxidative stress resistance, including peroxiredoxin PrxA, in response to hydrogen peroxide. In this study, we identified another OxyR homolog in V. cholerae, which we named OxyR2, and we renamed the previous OxyR OxyR1. We found that OxyR2 is required to activate its divergently transcribed gene ahpC, encoding an alkylhydroperoxide reductase, independently of H(2)O(2) A conserved cysteine residue in OxyR2 is critical for this function. Mutation of either oxyR2 or ahpC rendered V. cholerae more resistant to H(2)O(2) RNA sequencing analyses indicated that OxyR1-activated oxidative stress-resistant genes were highly expressed in oxyR2 mutants even in the absence of H(2)O(2) Further genetic analyses suggest that OxyR2-activated AhpC modulates OxyR1 activity by maintaining low intracellular concentrations of H(2)O(2) Furthermore, we showed that ΔoxyR2 and ΔahpC mutants were less fit when anaerobically grown bacteria were exposed to low levels of H(2)O(2) or incubated in seawater. These results suggest that OxyR2 and AhpC play important roles in the V. cholerae oxidative stress response.201728138024
34290.9514Heat-shock-increased survival to far-UV radiation in Escherichia coli is wavelength dependent. Heat-shock-induced resistance to far-UV (FUV) radiation was studied in Escherichia coli. The induction of FUV resistance was shown to be dependent on the products of the genes uvrA and polA in bacteria irradiated at 254 nm. Heat shock increased the resistance to 280 nm radiation in a uvrA6 recA13 mutant. Heat shock lowered the mutation frequency (reversion to tryptophan proficiency) in wild-type or uvrA strains irradiated at 254 nm. When these strains were irradiated at 280 nm, heat shock did not interfere with the mutation frequency in the wild-type strain, but greatly enhanced mutations in the uvrA mutant. After heat-shock treatment, the wild-type strain irradiated at 254 nm showed increased DNA degradation, indicating enhanced repair activity. However, heat shock did not stimulate SOS repair triggered by FUV. An increased survival of bacteriophages irradiated with FUV and inoculated into heat-shock-treated bacteria was not detected. The possibility that heat shock enhances excision repair activity in a wavelength-dependent manner is discussed.19948176549
617100.9513Lytic action of cloned pneumococcal phage lysis genes in Streptococcus pneumoniae. The genes hbl3, cpl1 and cpl7 coding for the pneumococcal phage lytic enzymes HBL3, CPL1 and CPL7, respectively, have been cloned into shuttle plasmids that can replicate in Streptococcus pneumoniae and Escherichia coli. All these genes were expressed in E. coli under the control of either the lytP promoter of the lytA gene, which codes for the major pneumococcal autolysin, or the promoter of the tetracycline-resistance gene (tetP). In contrast, cpl1 and cpl7 genes that code for lysozymes were expressed in pneumococcus only under the control of tetP, whereas the hbl3 gene that codes for an amidase can be expressed using either promoter. The phage lysozymes or amidase expressed in S. pneumoniae M31, a mutant deleted in the lytA gene coding for short chains, were placed under physiological control since these transformed bacteria grew as normal 'diplo' cells during the exponential phase and underwent autolysis only after long incubation at 37 degrees C. The lysis genes appear to be expressed constitutively in the transformed pneumococci, since sharply defined lysis of these cultures could be induced prematurely during the exponential phase of growth by addition of sodium deoxycholate.19938472929
125110.9510ROD1, a novel gene conferring multiple resistance phenotypes in Saccharomyces cerevisiae. Glutathione-dependent detoxification reactions are catalyzed by the enzyme glutathione S-transferase and are important in drug resistance in organisms ranging from bacteria to humans. The yeast Issatchenkia orientalis expresses a glutathione S-transferase (GST) protein that is induced when the GST substrate o-dinitrobenzene (o-DNB) is added to the culture. In this study, we show that overproduction of the I. orientalis GST in Saccharomyces cerevisiae leads to an increase in o-dinitrobenzene resistance in S. cerevisiae cells. To recover genes that influence o-DNB resistance in S. cerevisiae, a high copy plasmid library was screened for loci that elevate o-DNB tolerance. One gene was recovered and designated ROD1 (resistance to o-dinitrobenzene). This locus was found to encode a novel protein with no significant sequence similarity with proteins of known function in the data base. An epitope-tagged version of Rod1p was produced in S. cerevisiae and shown to function properly. Subcellular fractionation experiments indicated that this factor was found in the particulate fraction by differential centrifugation. Overproduction of Rod1p leads to resistance to not only o-DNB but also zinc and calcium. Strains that lack the ROD1 gene are hypersensitive to these same compounds. Rod1p represents a new type of molecule influencing drug tolerance in eukaryotes.19968621680
571120.9510Alternative periplasmic copper-resistance mechanisms in Gram negative bacteria. Bacteria have evolved different systems to tightly control both cytosolic and envelope copper concentration to fulfil their requirements and at the same time, avoid copper toxicity. We have previously demonstrated that, as in Escherichia coli, the Salmonella cue system protects the cytosol from copper excess. On the other hand, and even though Salmonella lacks the CusCFBA periplasmic copper efflux system, it can support higher copper concentrations than E. coli under anaerobic conditions. Here we show that the Salmonella cue regulon is also responsible for the control of copper toxicity in anaerobiosis. We establish that resistance in this condition requires a novel CueR-controlled gene named cueP. A DeltacueP mutant is highly susceptible to copper in the absence of oxygen, but shows a faint phenotype in aerobic conditions unless other copper-resistance genes are also deleted, resembling the E. coli CusCFBA behaviour. Species that contain a cueP homologue under CueR regulation have no functional CusR/CusS-dependent Cus-coding operon. Conversely, species that carry a CusR/CusS-regulated cus operon have no cueP homologues. Even more, we show that the CueR-controlled cueP expression increases copper resistance of a Deltacus E. coli. We posit that CueP can functionally replace the Cus complex for periplasmic copper resistance, in particular under anaerobic conditions.200919538445
559130.9509Coordinated regulation of chemotaxis and resistance to copper by CsoR in Pseudomonas putida. Copper is an essential enzyme cofactor in bacteria, but excess copper is highly toxic. Bacteria can cope with copper stress by increasing copper resistance and initiating chemorepellent response. However, it remains unclear how bacteria coordinate chemotaxis and resistance to copper. By screening proteins that interacted with the chemotaxis kinase CheA, we identified a copper-binding repressor CsoR that interacted with CheA in Pseudomonas putida. CsoR interacted with the HPT (P1), Dimer (P3), and HATPase_c (P4) domains of CheA and inhibited CheA autophosphorylation, resulting in decreased chemotaxis. The copper-binding of CsoR weakened its interaction with CheA, which relieved the inhibition of chemotaxis by CsoR. In addition, CsoR bound to the promoter of copper-resistance genes to inhibit gene expression, and copper-binding released CsoR from the promoter, leading to increased gene expression and copper resistance. P. putida cells exhibited a chemorepellent response to copper in a CheA-dependent manner, and CsoR inhibited the chemorepellent response to copper. Besides, the CheA-CsoR interaction also existed in proteins from several other bacterial species. Our results revealed a mechanism by which bacteria coordinately regulated chemotaxis and resistance to copper by CsoR.202540197389
544140.9509Organic Hydroperoxide Induces Prodigiosin Biosynthesis in Serratia sp. ATCC 39006 in an OhrR-Dependent Manner. The biosynthesis of prodigiosin in the model prodigiosin-producing strain, Serratia sp. ATCC 39006, is significantly influenced by environmental and cellular signals. However, a comprehensive regulatory mechanism for this process has not been well established. In the present study, we demonstrate that organic hydroperoxide activates prodigiosin biosynthesis in an OhrR-dependent manner. Specifically, the MarR-family transcriptional repressor OhrR (Ser39006_RS05455) binds to its operator located far upstream of the promoter region of the prodigiosin biosynthesis operon (319 to 286 nucleotides [nt] upstream of the transcription start site) and negatively regulates the expression of prodigiosin biosynthesis genes. Organic hydroperoxide disassociates the binding between OhrR and its operator, thereby promoting the prodigiosin production. Moreover, OhrR modulates the resistance of Serratia sp. ATCC 39006 to organic hydroperoxide by regulating the transcription of its own gene and the downstream cotranscribed ohr gene. These results demonstrate that OhrR is a pleiotropic repressor that modulates the prodigiosin production and the resistance of Serratia sp. ATCC 39006 to organic hydroperoxide stress. IMPORTANCE Bacteria naturally encounter various environmental and cellular stresses. Organic hydroperoxides generated from the oxidation of polyunsaturated fatty acids are widely distributed and usually cause lethal oxidative stress by damaging cellular components. OhrR is known as a regulator that modulates the resistance of bacteria to organic hydroperoxide stress. In the current study, organic hydroperoxide disassociates OhrR from the promoter of prodigiosin biosynthesis gene cluster, thus promoting transcription of pigA to -O genes. In this model, organic hydroperoxide acts as an inducer of prodigiosin synthesis in Serratia sp. ATCC 39006. These results improve our understanding of the regulatory network of prodigiosin synthesis and serve as an example for identifying the cross talk between the stress responses and the regulation of secondary metabolism.202235044847
41150.9509Rice WRKY13 regulates cross talk between abiotic and biotic stress signaling pathways by selective binding to different cis-elements. Plants use a complex signal transduction network to regulate their adaptation to the ever-changing environment. Rice (Oryza sativa) WRKY13 plays a vital role in the cross talk between abiotic and biotic stress signaling pathways by suppressing abiotic stress resistance and activating disease resistance. However, it is not clear how WRKY13 directly regulates this cross talk. Here, we show that WRKY13 is a transcriptional repressor. During the rice responses to drought stress and bacterial infection, WRKY13 selectively bound to certain site- and sequence-specific cis-elements on the promoters of SNAC1 (for STRESS RESPONSIVE NO APICAL MERISTEM, ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR1/2, CUP-SHAPED COTYLEDON), the overexpression of which increases drought resistance, and WRKY45-1, the knockout of which increases both bacterial disease and drought resistance. WRKY13 also bound to two cis-elements of its native promoter to autoregulate the balance of its gene expression in different physiological activities. WRKY13 was induced in leaf vascular tissue, where bacteria proliferate, during infection, and in guard cells, where the transcriptional factor SNAC1 enhances drought resistance, during both bacterial infection and drought stress. These results suggest that WRKY13 regulates the antagonistic cross talk between drought and disease resistance pathways by directly suppressing SNAC1 and WRKY45-1 and autoregulating its own expression via site- and sequence-specific cis-elements on the promoters of these genes in vascular tissue where bacteria proliferate and guard cells where the transcriptional factor SNAC1 mediates drought resistance by promoting stomatal closure.201324130197
520160.9509Respiratory chain components are required for peptidoglycan recognition protein-induced thiol depletion and killing in Bacillus subtilis and Escherichia coli. Mammalian peptidoglycan recognition proteins (PGRPs or PGLYRPs) kill bacteria through induction of synergistic oxidative, thiol, and metal stress. Tn-seq screening of Bacillus subtilis transposon insertion library revealed that mutants in the shikimate pathway of chorismate synthesis had high survival following PGLYRP4 treatment. Deletion mutants for these genes had decreased amounts of menaquinone (MK), increased resistance to killing, and attenuated depletion of thiols following PGLYRP4 treatment. These effects were reversed by MK or reproduced by inhibiting MK synthesis. Deletion of cytochrome aa(3)-600 or NADH dehydrogenase (NDH) genes also increased B. subtilis resistance to PGLYRP4-induced killing and attenuated thiol depletion. PGLYRP4 treatment also inhibited B. subtilis respiration. Similarly in Escherichia coli, deletion of ubiquinone (UQ) synthesis, formate dehydrogenases (FDH), NDH-1, or cytochrome bd-I genes attenuated PGLYRP4-induced thiol depletion. PGLYRP4-induced low level of cytoplasmic membrane depolarization in B. subtilis and E. coli was likely not responsible for thiol depletion. Thus, our results show that the respiratory electron transport chain components, cytochrome aa(3)-600, MK, and NDH in B. subtilis, and cytochrome bd-I, UQ, FDH-O, and NDH-1 in E. coli, are required for both PGLYRP4-induced killing and thiol depletion and indicate conservation of the PGLYRP4-induced thiol depletion and killing mechanisms in Gram-positive and Gram-negative bacteria.202133420211
542170.9508Role of Yops and adhesins in resistance of Yersinia enterocolitica to phagocytosis. Yersinia enterocolitica is a pathogen endowed with two adhesins, Inv and YadA, and with the Ysc type III secretion system, which allows extracellular adherent bacteria to inject Yop effectors into the cytosol of animal target cells. We tested the influence of all of these virulence determinants on opsonic and nonopsonic phagocytosis by PU5-1.8 and J774 mouse macrophages, as well as by human polymorphonuclear leukocytes (PMNs). The adhesins contributed to phagocytosis in the absence of opsonins but not in the presence of opsonins. In agreement with previous results, YadA counteracted opsonization. In every instance, the Ysc-Yop system conferred a significant level of resistance to phagocytosis. Nonopsonized single-mutant bacteria lacking either YopE, -H, -T, or -O were phagocytosed significantly more by J774 cells and by PMNs. Opsonized bacteria were phagocytosed more than nonopsonized bacteria, and mutant bacteria lacking either YopH, -T, or -O were phagocytosed significantly more by J774 cells and by PMNs than were wild-type (WT) bacteria. Opsonized mutants lacking only YopE were phagocytosed significantly more than were WT bacteria by PMNs but not by J774 cells. Thus, YopH, -T, and -O were involved in all of the phagocytic processes studied here but YopE did not play a clear role in guarding against opsonic phagocytosis by J774. Mutants lacking YopP and YopM were, in every instance, as resistant as WT bacteria. Overexpression of YopE, -H, -T, or -O alone did not confer resistance to phagocytosis, although it affected the cytoskeleton. These results show that YopH, YopT, YopO, and, in some instances, YopE act synergistically to increase the resistance of Y. enterocolitica to phagocytosis by macrophages and PMNs.200212117925
574180.9506Pyrroloquinoline quinone and a quinoprotein kinase support γ-radiation resistance in Deinococcus radiodurans and regulate gene expression. Deinococcus radiodurans is known for its extraordinary resistance to various DNA damaging agents including γ-radiation and desiccation. The pqqE:cat and Δdr2518 mutants making these cells devoid of pyrroloquinoline quinone (PQQ) and a PQQ inducible Ser/Thr protein kinase, respectively, became sensitive to γ-radiation. Transcriptome analysis of these mutants showed differential expression of the genes including those play roles in oxidative stress tolerance and (DSB) repair in D. radiodurans and in genome maintenance and stress response in other bacteria. Escherichia coli cells expressing DR2518 and PQQ showed improved resistance to γ-radiation, which increased further when both DR2518 and PQQ were present together. Although, profiles of genes getting affected in these mutants were different, there were still a few common genes showing similar expression trends in both the mutants and some others as reported earlier in oxyR and pprI mutant of this bacterium. These results suggested that PQQ and DR2518 have independent roles in γ-radiation resistance of D. radiodurans but their co-existence improves radioresistance further, possibly by regulating differential expression of the genes important for bacterial response to oxidative stress and DNA damage.201322961447
8742190.9506Effect of Bacteria and Bacterial Constituents on Recovery and Resistance of Tulane Virus. Noroviruses encounter numerous and diverse bacterial populations in the host and environment, but the impact of bacteria on norovirus transmission, infection, detection, and inactivation are not well understood. Tulane virus (TV), a human norovirus surrogate, was exposed to viable bacteria, bacterial metabolic products, and bacterial cell constituents and was evaluated for impact on viral recovery, propagation, and inactivation resistance, respectively. TV was incubated with common soil, intestinal, skin, and phyllosphere bacteria, and unbound viruses were recovered by centrifugation and filtration. TV recovery from various bacterial suspensions was not impeded, which suggests a lack of direct, stable binding between viruses and bacteria. The cell-free supernatant (CFS) of Bifidobacterium bifidum 35914, a bacterium that produces glycan-modifying enzymes, was evaluated for effect on the propagation of TV in LLC-MK2 cells. CFS did not limit TV propagation relative to TV absent of CFS. The impact of Escherichia coli O111:B4 lipopolysaccharide (LPS) and Bacillus subtilis peptidoglycan (PEP) on TV thermal and chlorine inactivation resistance was evaluated. PEP increased TV thermal and chlorine inactivation resistance compared with control TV in phosphate-buffered saline (PBS). TV suspended in PBS and LPS was reduced by more than 3.7 log at 60°C, whereas in PEP, TV reduction was approximately 2 log. Chlorine treatment (200 ppm) rendered TV undetectable (>3-log reduction) in PBS and LPS; however, TV was still detected in PEP, reduced by 2.9 log. Virus inactivation studies and food processing practices should account for potential impact of bacteria on viral resistance.202032221571