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81700.9910Mercury resistance transposons in Bacilli strains from different geographical regions. A total of 65 spore-forming mercury-resistant bacteria were isolated from natural environments worldwide in order to understand the acquisition of additional genes by and dissemination of mercury resistance transposons across related Bacilli genera by horizontal gene movement. PCR amplification using a single primer complementary to the inverted repeat sequence of TnMERI1-like transposons showed that 12 of 65 isolates had a transposon-like structure. There were four types of amplified fragments: Tn5084, Tn5085, Tn(d)MER3 (a newly identified deleted transposon-like fragment) and Tn6294 (a newly identified transposon). Tn(d)MER3 is a 3.5-kb sequence that carries a merRETPA operon with no merB or transposase genes. It is related to the mer operon of Bacillus licheniformis strain FA6-12 from Russia. DNA homology analysis shows that Tn6294 is an 8.5-kb sequence that is possibly derived from Tn(d)MER3 by integration of a TnMERI1-type transposase and resolvase genes and in addition the merR2 and merB1 genes. Bacteria harboring Tn6294 exhibited broad-spectrum mercury resistance to organomercurial compounds, although Tn6294 had only merB1 and did not have the merB2 and merB3 sequences for organomercurial lyases found in Tn5084 of B. cereus strain RC607. Strains with Tn6294 encode mercuric reductase (MerA) of less than 600 amino acids in length with a single N-terminal mercury-binding domain, whereas MerA encoded by strains MB1 and RC607 has two tandem domains. Thus, Tn(d)MER3 and Tn6294 are shorter prototypes for TnMERI1-like transposons. Identification of Tn6294 in Bacillus sp. from Taiwan and in Paenibacillus sp. from Antarctica indicates the wide horizontal dissemination of TnMERI1-like transposons across bacterial species and geographical barriers.201626802071
81510.9905The sequence of the mer operon of pMER327/419 and transposon ends of pMER327/419, 330 and 05. Three different, independently isolated mercury-resistance-conferring plasmids, pMER327/419, pMER330 and pMER05, from cultures originating from the river Mersey (UK), contain identical regulatory merR genes and transposon ends. The mer determinant from pMER327/419 contains an additional potential ORF (ORF F) located between merP and merA when compared with the archetypal Tn501. Although these plasmids confer narrow-spectrum resistance (resistance to Hg2+, but not organomercurials) their merR genes encode a potential organomercurial-sensing protein. Transposition of the mer of pMER05 into plasmid RP4 was demonstrated and, as with Tn502 and Tn5053, insertion occurred at a specific region. The sequence of pMER05 is identical at the 'left' and 'right' termini and across merR to Tn5053, which was independently isolated from the chromosome of a Xanthomonas sp. bacteria from the Khaidarkan mercury mine in Kirgizia, former Soviet Union [Kholodii et al., J. Mol. Biol. 230 (1993a) 1103-1107]. The transpositional unit of pMER05 is, like that of Tn5053, bounded by DNA homologous to the imperfect 25-bp inverted repeats (IR) of the In2 integron, which brackets antibiotic-resistance cassettes in Tn21 subgroup transposons. At one end of the transposable element, and internal to the In2-like IR, is a 38-bp IR which closely resembles the IR that bounds Tn21.19948063107
53020.9898Location of the genes for anthranilate synthase in Streptomyces venezuelae ISP5230: genetic mapping after integration of the cloned genes. The anthranilate synthase (trpEG) genes in Streptomyces venezuelae ISP5230 were located by allowing a segregationally unstable plasmid carrying cloned S. venezuelae trpEG DNA and a thiostrepton resistance (tsr) marker to integrate into the chromosome. The integrated tsr was mapped by conjugation and transduction to a location close to tyr-2, between arg-6 and trpA13. A genomic DNA fragment containing trpC from S. venezuelae ISP5230 was cloned by complementation of a trpC mutation in Streptomyces lividans. Evidence from restriction enzyme analysis of the cloned DNA fragments, from Southern hybridization using the cloned trp DNA as probes, and from cotransduction frequencies, placed trpEG at a distance of 12-45 kb from the trpCBA cluster. The overall arrangement of tryptophan biosynthesis genes in the S. venezuelae chromosome differs from that in other bacteria examined so far.19938515229
40330.9897Nucleotide sequence and expression of the mercurial-resistance operon from Staphylococcus aureus plasmid pI258. The mercurial-resistance determinant from Staphylococcus aureus plasmid pI258 is located on a 6.4-kilobase-pair Bgl II fragment. The determinant was cloned into both Bacillus subtilis and Escherichia coli. Mercury resistance was found only in B. subtilis. The 6404-base-pair DNA sequence of the Bgl II fragment was determined. The mer DNA sequence includes seven open reading frames, two of which have been identified by homology with the merA (mercuric reductase) and merB (organomercurial lyase) genes from the mercurial-resistance determinants of Gram-negative bacteria. Whereas 40% of the amino acid residues overall were identical between the pI258 merA polypeptide product and mercuric reductases from Gram-negative bacteria, the percentage identity in the active-site positions and those thought to be involved in NADPH and FAD contacts was above 90%. The 216 amino acid organomercurial lyase sequence was 39% identical with that from a Serratia plasmid, with higher conservation in the middle of the sequences and lower homologies at the amino and carboxyl termini. The remaining five open reading frames in the pI258 mer sequence have no significant homologies with the genes from previously sequenced Gram-negative mer operons.19873037534
81940.9894Trimethoprim resistance transposon Tn4003 from Staphylococcus aureus encodes genes for a dihydrofolate reductase and thymidylate synthetase flanked by three copies of IS257. Trimethoprim resistance mediated by the Staphylococcus aureus multi-resistance plasmid pSK1 is encoded by a structure with characteristics of a composite transposon which we have designated Tn4003. Nucleotide sequence analysis of Tn4003 revealed it to be 4717 bp in length and to contain three copies of the insertion element IS257 (789-790 bp), the outside two of which are flanked by directly repeated 8-bp target sequences. IS257 has imperfect terminal inverted repeats of 27-28 bp and encodes for a putative transposase with two potential alpha-helix-turn-alpha-helix DNA recognition motifs. IS257 shares sequence similarities with members of the IS15 family of insertion sequences from Gram-negative bacteria and with ISS1 from Streptococcus lactis. The central region of the transposon contains the dfrA gene that specifies the S1 dihydrofolate reductase (DHFR) responsible for trimethoprim resistance. The S1 enzyme shows sequence homology with type I and V trimethoprim-resistant DHFRs from Gram-negative bacteria and with chromosomally encoded DHFRs from Gram-positive and Gram-negative bacteria. 5' to dfrA is a thymidylate synthetase gene, designated thyE.19892548057
49150.9892Class II broad-spectrum mercury resistance transposons in Gram-positive bacteria from natural environments. We have studied the mechanisms of the horizontal dissemination of a broad-spectrum mercury resistance determinant among Bacillus and related species. This mer determinant was first described in Bacillus cereus RC607 from Boston Harbor, USA, and was then found in various Bacillus and related species in Japan, Russia and England. We have shown that the mer determinant can either be located at the chromosome, or on a plasmid in the Bacillus species, and is carried by class II mercury resistance transposons: Tn5084 from B. cereus RC607 and B. cereus VKM684 (ATCC10702) and Tn5085 from Exiguobacterium sp. TC38-2b. Tn5085 is identical in nucleotide sequence to TnMERI1, the only other known mer transposon from Bacillus species, but it does not contain an intron like TnMERI1. Tn5085 is functionally active in Escherichia coli. Tn5083, which we have isolated from B. megaterium MK64-1, contains an RC607-like mer determinant, that has lost some mercury resistance genes and possesses a merA gene which is a novel sequence variant that has not been previously described. Tn5083 and Tn5084 are recombinants, and are comprised of fragments from several transposons including Tn5085, and a relative of a putative transposon from B. firmus (which contains similar genes to the cadmium resistance operon of Staphylococcus aureus), as well as others. The sequence data showed evidence for recombination both between transposition genes and between mer determinants.200111446519
49460.9889The mercury resistance operon of the IncJ plasmid pMERPH exhibits structural and regulatory divergence from other Gram-negative mer operons. The bacterial mercury resistance determinant carried on the IncJ plasmid pMERPH has been characterized further by DNA sequence analysis. From the sequence of a 4097 bp Bg/II fragment which confers mercury resistance, it is predicted that the determinant consists of the genes merT, merP, merC and merA. The level of DNA sequence similarity between these genes and those of the mer determinant of Tn21 was between 56 center dot 4 and 62 center dot 4%. A neighbour-joining phylogenetic tree of merA gene sequences was constructed which suggested that pMERPH bears the most divergent Gram-negative mer determinant characterized to date. Although the determinant from pMERPH has been shown to be inducible, no regulatory genes have been found within the Bg/II fragment and it is suggested that a regulatory gene may be located elsewhere on the plasmid. The cloned determinant has been shown to express mercury resistance constitutively. Analysis of the pMERPH mer operator/promoter (O/P) region in vivo has shown constitutive expression from the mer PTCPA promoter, which could be partially repressed by the presence of a trans-acting MerR protein from a Tn21-like mer determinant. This incomplete repression of mer PTCPA promoter activity may be due to the presence of an extra base between the -35 and -10 sequences of the promoter and/or to variation in the MerR binding sites in the O/P region. Expression from the partially repressed mer PTCPA promoter could be restored by the addition of inducing levels of Hg2+ ions. Using the polymerase chain reaction with primers designed to amplify regions in the merP and merA genes, 1 center dot 37 kb pMERPH-like sequences have been amplified from the IncJ plasmid R391, the environmental isolate SE2 and from DNA isolated directly from non-cultivated bacteria in River Mersey sediment. This suggests that pMERPH-like sequences, although rare, are nevertheless persistent in natural environments.19968932707
40470.9886Plasmid-borne cadmium resistance genes in Listeria monocytogenes are similar to cadA and cadC of Staphylococcus aureus and are induced by cadmium. pLm74 is the smallest known plasmid in Listeria monocytogenes. It confers resistance to the toxic divalent cation cadmium. It contains a 3.1-kb EcoRI fragment which hybridizes with the cadAC genes of plasmid pI258 of Staphylococcus aureus. When introduced into cadmium-sensitive L. monocytogenes or Bacillus subtilis strains, this fragment conferred cadmium resistance. The DNA sequence of the 3.1-kb EcoRI fragment contains two open reading frames, cadA and cadC. The deduced amino acid sequences are similar to those of the cad operon of plasmid pI258 of S. aureus, known to prevent accumulation of Cd2+ in the bacteria by an ATPase efflux mechanism. The cadmium resistance determinant of L. monocytogenes does not confer zinc resistance, in contrast to the cadAC determinant of S. aureus, suggesting that the two resistance mechanisms are slightly different. Slot blot DNA-RNA hybridization analysis showed cadmium-inducible synthesis of L. monocytogenes cadAC RNA.19948188605
82080.9886Nucleotide sequence analysis of a transposon (Tn5393) carrying streptomycin resistance genes in Erwinia amylovora and other gram-negative bacteria. A class II Tn3-type transposable element, designated Tn5393 and located on plasmid pEa34 from streptomycin-resistant strain CA11 of Erwinia amylovora, was identified by its ability to move from pEa34 to different sites in plasmids pGEM3Zf(+) and pUCD800. Nucleotide sequence analysis reveals that Tn5393 consists of 6,705 bp with 81-bp terminal inverted repeats and generates 5-bp duplications of the target DNA following insertion. Tn5393 contains open reading frames that encode a putative transposase (tnpA) and resolvase (tnpR) of 961 and 181 amino acids, respectively. The two open reading frames are separated by a putative recombination site (res) consisting of 194 bp. Two streptomycin resistance genes, strA and strB, were identified on the basis of their DNA sequence homology to streptomycin resistance genes in plasmid RSF1010. StrA is separated from tnpR by a 1.2-kb insertion element designated IS1133. The tnpA-res-tnpR region of Tn5393 was detected in Pseudomonas syringae pv. papulans Psp36 and in many other gram-negative bacteria harboring strA and strB. Except for some strains of Erwinia herbicola, these other gram-negative bacteria lacked insertion sequence IS1133. The prevalence of strA and strB could be accounted for by transposition of Tn5393 to conjugative plasmids that are then disseminated widely among gram-negative bacteria.19938380801
53190.9886p-Aminobenzoic acid and chloramphenicol biosynthesis in Streptomyces venezuelae: gene sets for a key enzyme, 4-amino-4-deoxychorismate synthase. Amplification of sequences from Streptomyces venezuelae ISP5230 genomic DNA using PCR with primers based on conserved prokaryotic pabB sequences gave two main products. One matched pabAB, a locus previously identified in S. venezuelae. The second closely resembled the conserved pabB sequence consensus and hybridized with a 3.8 kb NcoI fragment of S. venezuelae ISP5230 genomic DNA. Cloning and sequence analysis of the 3.8 kb fragment detected three ORFs, and their deduced amino acid sequences were used in BLAST searches of the GenBank database. The ORF1 product was similar to PabB in other bacteria and to the PabB domain encoded by S. venezuelae pabAB. The ORF2 product resembled PabA of other bacteria. ORF3 was incomplete; its deduced partial amino acid sequence placed it in the MocR group of GntR-type transcriptional regulators. Introducing vectors containing the 3.8 kb NcoI fragment of S. venezuelae DNA into pabA and pabB mutants of Escherichia coli, or into the Streptomyces lividans pab mutant JG10, enhanced sulfanilamide resistance in the host strains. The increased resistance was attributed to expression of the pair of discrete translationally coupled p-aminobenzoic acid biosynthesis genes (designated pabB/pabA) cloned in the 3.8 kb fragment. These represent a second set of genes encoding 4-amino-4-deoxychorismate synthase in S. venezuelae ISP5230. In contrast to the fused pabAB set previously isolated from this species, they do not participate in chloramphenicol biosynthesis, but like pabAB they can be disrupted without affecting growth on minimal medium. The gene disruption results suggest that S. venezuelae may have a third set of genes encoding PABA synthase.200111495989
366100.9886Genes encoding mercuric reductases from selected gram-negative aquatic bacteria have a low degree of homology with merA of transposon Tn501. An investigation of the Hg2+ resistance mechanism of four freshwater and four coastal marine bacteria that did not hybridize with a mer operonic probe was conducted (T. Barkay, C. Liebert, and M. Gillman, Appl. Environ. Microbiol. 55:1196-1202, 1989). Hybridization with a merA probe, the gene encoding the mercuric reductase polypeptide, at a stringency of hybridization permitting hybrid formation between evolutionarily distant merA genes (as exists between gram-positive and -negative bacteria), detected merA sequences in the genomes of all tested strains. Inducible Hg2+ volatilization was demonstrated for all eight organisms, and NADPH-dependent mercuric reductase activities were detected in crude cell extracts of six of the strains. Because these strains represented random selections of bacteria from three aquatic environments, it is concluded that merA encodes a common molecular mechanism for Hg2+ resistance and volatilization in aerobic heterotrophic aquatic communities.19902166470
816110.9881High-Level Nickel Resistance in Alcaligenes xylosoxydans 31A and Alcaligenes eutrophus KTO2. Two new nickel-resistant strains of Alcaligenes species were selected from a large number (about 400) of strains isolated from ecosystems polluted by heavy metals and were studied on the physiological and molecular level. Alcaligenes xylosoxydans 31A is a heterotrophic bacterium, and Alcaligenes eutrophus KTO2 is an autotrophic aerobic hydrogen-oxidizing bacterium. Both strains carry-among other plasmids-a megaplasmid determining resistance to 20 to 50 mM NiCl(2) and 20 mM CoCl(2) (when growing in defined Tris-buffered media). Megaplasmids pTOM8, pTOM9 from strain 31A, and pGOE2 from strain KTO2 confer nickel resistance to the same degree to transconjugants of all strains of A. eutrophus tested but were not transferred to Escherichia coli. However, DNA fragments carrying the nickel resistance genes, cloned into broad-hostrange vector pVDZ'2, confer resistance to A. eutrophus derivatives as well as E. coli. The DNA fragments of both bacteria, TBA8, TBA9, and GBA (14.5-kb BamHI fragments), appear to be identical. They share equal size, restriction maps, and strong DNA homology but are largely different from fragment HKI of nickel-cobalt resistance plasmid pMOL28 of A. eutrophus CH34.199116348590
176120.9879The mercury resistance (mer) operon in a marine gliding flavobacterium, Tenacibaculum discolor 9A5. Genes conferring mercury resistance have been investigated in a variety of bacteria and archaea but not in bacteria of the phylum Bacteroidetes, despite their importance in many environments. We found, however, that a marine gliding Bacteroidetes species, Tenacibaculum discolor, was the predominant mercury-resistant bacterial taxon cultured from a salt marsh fertilized with mercury-contaminated sewage sludge. Here we report characterization of the mercuric reductase and the narrow-spectrum mercury resistance (mer) operon from one of these strains - T. discolor 9A5. This mer operon, which confers mercury resistance when cloned into Flavobacterium johnsoniae, encodes a novel mercury-responsive ArsR/SmtB family transcriptional regulator that appears to have evolved independently from other mercury-responsive regulators, a novel putative transport protein consisting of a fusion between the integral membrane Hg(II) transporter MerT and the periplasmic Hg(II)-binding protein MerP, an additional MerP protein, and a mercuric reductase that is phylogenetically distinct from other known mercuric reductases.201322816663
178130.9878Molecular basis of bacterial resistance to organomercurial and inorganic mercuric salts. Bacteria mediate resistance to organomercurial and inorganic mercuric salts by metabolic conversion to nontoxic elemental mercury, Hg(0). The genes responsible for mercury resistance are organized in the mer operon, and such operons are often found in plasmids that also bear drug resistance determinants. We have subcloned three of these mer genes, merR, merB, and merA, and have studied their protein products via protein overproduction and purification, and structural and functional characterization. MeR is a metalloregulatory DNA-binding protein that acts as a repressor of both its own and structural gene transcription in the absence of Hg(II); in addition it acts as a positive effector of structural gene transcription when Hg(II) is present. MerB, organomercury lyase, catalyzes the protonolytic fragmentation of organomercurials to the parent hydrocarbon and Hg(II) by an apparent SE2 mechanism. MerA, mercuric ion reductase, is an FAD-containing and redox-active disulfide-containing enzyme with homology to glutathione reductase. It has evolved the unique catalytic capacity to reduce Hg(II) to Hg(0) and thereby complete the detoxification scheme.19883277886
490140.9878Mercuric resistance genes in gram-positive oral bacteria. Mercury-resistant bacteria isolated from the oral cavities of children carried one of two types of merA gene that appear to have evolved from a common ancestor. Streptococcus oralis, Streptococcus mitis and a few other species had merA genes that were very similar to merA of Bacillus cereus strain RC607. Unlike the B. cereus RC607 merA gene, however, the streptococcal merA genes were not carried on Tn5084-like transposons. Instead, comparisons with microbial genomic sequences suggest the merA gene is located on a novel type II transposon. Coagulase-negative staphylococci and Streptococcus parasanguis had identical merA genes that represent a new merA variant.200415251199
492150.9878Identification of A Novel Arsenic Resistance Transposon Nested in A Mercury Resistance Transposon of Bacillus sp. MB24. A novel TnMERI1-like transposon designated as TnMARS1 was identified from mercury resistant Bacilli isolated from Minamata Bay sediment. Two adjacent ars operon-like gene clusters, ars1 and ars2, flanked by a pair of 78-bp inverted repeat sequences, which resulted in a 13.8-kbp transposon-like fragment, were found to be sandwiched between two transposable genes of the TnMERI1-like transposon of a mercury resistant bacterium, Bacillus sp. MB24. The presence of a single transcription start site in each cluster determined by 5'-RACE suggested that both are operons. Quantitative real time RT-PCR showed that the transcription of the arsR genes contained in each operon was induced by arsenite, while arsR2 responded to arsenite more sensitively and strikingly than arsR1 did. Further, arsenic resistance complementary experiments showed that the ars2 operon conferred arsenate and arsenite resistance to an arsB-knocked out Bacillus host, while the ars1 operon only raised arsenite resistance slightly. This transposon nested in TnMARS1 was designated as TnARS1. Multi-gene cluster blast against bacteria and Bacilli whole genome sequence databases suggested that TnMARS1 is the first case of a TnMERI1-like transposon combined with an arsenic resistance transposon. The findings of this study suggested that TnMERI1-like transposons could recruit other mobile elements into its genetic structure, and subsequently cause horizontal dissemination of both mercury and arsenic resistances among Bacilli in Minamata Bay.201931744069
374160.9877Simultaneous detection and removal of organomercurial compounds by using the genetic expression system of an organomercury lyase from the transposon Tn MERI1. Using a newly identified organomercury lyase gene (merB3) expression system from Tn MERI1, the mercury resistance transposon first found in Gram-positive bacteria, a dual-purpose system to detect and remove organomercurial contamination was developed. A plasmid was constructed by fusing the promoterless luxAB genes as bioluminescence reporter genes downstream of the merB3 gene and its operator/promoter region. Another plasmid, encoding mer operon genes from merR1 to merA, was also constructed to generate an expression regulatory protein, MerR1, and a mercury reductase enzyme, MerA. These two plasmids were transformed into Escherichia coli cells to produce a biological system that can detect and remove environmental organomercury contamination. Organomercurial compounds, such as neurotoxic methylmercury at nanomolar levels, were detected using the biomonitoring system within a few minutes and were removed during the next few hours.200212073137
407170.9876Molecular cloning and characterization of two lincomycin-resistance genes, lmrA and lmrB, from Streptomyces lincolnensis 78-11. Two different lincomycin-resistance determinants (lmrA and lmrB) from Streptomyces lincolnensis 78-11 were cloned in Streptomyces lividans 66 TK23. The gene lmrA was localized on a 2.16 kb fragment, the determined nucleotide sequence of which encoded a single open reading frame 1446 bp long. Analysis of the deduced amino acid sequence suggested the presence of 12 membrane-spanning domains and showed significant similarities to the methylenomycin-resistance protein (Mmr) from Streptomyces coelicolor, the QacA protein from Staphylococcus aureus, and several tetracycline-resistance proteins from both Gram-positive and Gram-negative bacteria, as well as to some sugar-transport proteins from Escherichia coli. The lmrB gene was actively expressed from a 2.7 kb fragment. An open reading frame of 837 bp could be localized which encoded a protein that was significantly similar to 23S rRNA adenine(2058)-N-methyltransferases conferring macrolide-lincosamide-streptogramin resistance. LmrB also had putative rRNA methyltransferase activity since lincomycin resistance of ribosomes was induced in lmrB-containing strains. Surprisingly, both enzymes, LmrA and LmrB, had a substrate specificity restricted to lincomycin and did not cause resistance to other lincosamides such as celesticetin and clindamycin, or to macrolides.19921328813
493180.9875Mercury resistance transposons of gram-negative environmental bacteria and their classification. A total of 29 mercury resistance transposons were isolated from mercury-resistant environmental strains of proteobacteria collected in different parts of Eurasia and the USA and tested for hybridization with probes specific for transposase genes of known mercury resistance transposons. 9 were related to Tn21 in this test, 12 were related to Tn5053, 4 to Tn5041 and 1 to Tn5044; three transposons were negative in this test. Restriction mapping and DNA sequencing revealed that 12 transposons were identical or nearly identical to their corresponding relatives while the rest showed varying divergence from their closest relatives. Most of these previously unknown transposons apparently arose as a result of homologous or site-specific recombination. One of these, Tn5046, was completely sequenced, and shown to be a chimera with the mer operon and the transposition module derived from the transposons related to Tn5041 and to Tn5044, respectively. Transposon Tn5070, showing no hybridization with the specific probes used in this study, was also completely sequenced. The transposition module of Tn5070 was most closely related to that of Tn3 while the mer operon was most closely related to that of plasmid pMERPH. The merR of Tn5070 is transcribed in the same direction as the mer structural genes, which is typical for mer operons of gram-positive bacteria. Our data suggest that environmental bacteria may harbor many not yet recognized mercury resistance transposons and warrant their further inventory.200111763242
375190.9873A mariner transposon vector adapted for mutagenesis in oral streptococci. This article describes the construction and characterization of a mariner-based transposon vector designed for use in oral streptococci, but with a potential use in other Gram-positive bacteria. The new transposon vector, termed pMN100, contains the temperature-sensitive origin of replication repATs-pWV01, a selectable kanamycin resistance gene, a Himar1 transposase gene regulated by a xylose-inducible promoter, and an erythromycin resistance gene flanked by himar inverted repeats. The pMN100 plasmid was transformed into Streptococcus mutans UA159 and transposon mutagenesis was performed via a protocol established to perform high numbers of separate transpositions despite a low frequency of transposition. The distribution of transposon inserts in 30 randomly picked mutants suggested that mariner transposon mutagenesis is unbiased in S. mutans. A generated transposon mutant library containing 5000 mutants was used in a screen to identify genes involved in the production of sucrose-dependent extracellular matrix components. Mutants with transposon inserts in genes encoding glycosyltransferases and the competence-related secretory locus were predominantly found in this screen.201424753509