Identification and characterization of genes encoding sex pheromone cAM373 activity in Enterococcus faecalis and Staphylococcus aureus

The sex pheromone cAM373 of Enterococcus faecalis and the related staph -cAM373 of Staphylococcus aureus were found to correspond to heptapeptides located within the C-termini of the signal sequences of putative prelipoproteins. The deduced mature forms of the lipoproteins share no detectable homology and presumably serve unrelated functions in the cells. The chromosomally encoded genetic determinants for production of the pheromones have been identified and designated camE (encoding cAM373) and camS (encoding staph -cAM373). Truncated and full-length clones of camE were generated in Escherichia coli , in which cAM373 activity was expressed. In E. faecalis , insertional inactivation in the middle of camE had no detectable phenotypic effects on the pheromone system. Establishment of an in frame translation stop codon within the signal sequence resulted in reduction of cAM373 activity to 3% of normal levels. The camS determinant has homologues in Staphylococcus epidermidis , Bacillus subtilis and Listeria monocytogenes ; however, corresponding heptapeptides present within those sequences do not resemble staph -cAM373 closely. The particular significance of staph -cAM373 as a potential intergeneric inducer of transfer-proficient genetic elements is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75605/1/j.1365-2958.2002.02922.x.pd

Enterococcal sex pheromone precursors are part of signal sequences for surface lipoproteins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73811/1/j.1365-2958.2000.01687.x.pd

Enterococcal sex pheromone precursors are part of signal sequences for surface lipoproteins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73811/1/j.1365-2958.2000.01687.x.pd

Plasmid pAMS1-Encoded, Bacteriocin-Related “Siblicide” in Enterococcus faecalis▿

The Enterococcus faecalis class IIa bacteriocin MC4-1 encoded by the sex pheromone-responding, multiple-antibiotic resistance plasmid pAMS1 exhibits “siblicidal” (sibling-killing) activity under certain conditions. Stabs of plasmid-containing cells on solid medium containing lawns of bacteria of the same (plasmid-containing) strain give rise to zones of inhibition. If the plasmid-containing host also produces gelatinase, bacteriocin cannot be detected

Nucleotide Sequence of the 18-kb Conjugative Transposon Tn916 from Enterococcus faecalis

Conjugative transposon Tn916 from Enterococcus faecalis DS16 encodes tetracycline resistance (Tet M) as well as determinants necessary for its own movement. Determination of the nucleotide sequence of Tn916 has been completed. The element is 18,032 bp in length and has an overall G+C content of 38.8%. Twenty-four potential open reading frames (ORFs) were identified based on sequence analysis. Similarities of the ORFs to other known determinants, which were revealed by database searches, are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31215/1/0000117.pd

Plasmid Content of a Vancomycin-Resistant Enterococcus faecalis Isolate from a Patient Also Colonized by Staphylococcus aureus with a VanA Phenotype

Vancomycin-resistant Enterococcus faecalis coisolated with vancomycin-resistant (VanA) Staphylococcus aureus was found to contain two plasmids, designated pAM830 (45 kb) and pAM831 (95 kb). pAM830, found to be conjugative and closely related to the Inc18 family of broad-host-range conjugative plasmids, encodes resistances to vancomycin (via a Tn1546-like element) and erythromycin; pAM831 encodes resistances to gentamicin, streptomycin, and erythromycin

Indication of Transposition of a Mobile DNA Element Containing the vat(D) and erm(B) Genes in Enterococcus faecium

The vat(D) and erm(B) genes encoding streptogramin resistance in Enterococcus faecium transferred together, and a direct physical link between erm(B) and vat(D) was detected. Both the vat(D) and erm(B) probes hybridized to fragments of different sizes in the donor and transconjugants, which indicated a transposition event

Targeting Cariogenic Streptococcus mutans in Oral Biofilms with Charge-Switching Smart Antimicrobial Polymers

Cariogenic biofilms produce strong acidic microenvironments, which is the primary cause of dental caries. Streptococcus mutans is a dominant species in cariogenic biofilms. Herein, we report a pH-responsive, charge-switching smart copolymer to selectively target and eradicate bacteria in cariogenic biofilms. To that end, the copolymer is designed to be activated in an acidic environment. The smart copolymer, Poly-1A, consists of ternary compositions of monomers with a cationic ethyl ammonium group, a carboxylic group, and a hydrophobic group in the side chains. The net charge of Poly-1A was charge neutral at neutral pH, but it switched to be cationic because the acidic carboxylate side chains were protonated and became neutral; however, the ammonium groups remained positive. Poly-1A with a net positive charge bound to the anionic surface of oral bacteria by electrostatic interactions and disrupted the bacterial membranes, causing bacterial death. Poly-1A reduced the cell viability of planktonic and biofilm S. mutans at pH 4.5, while it was not bactericidal at pH 7.4. Poly-1A did not reduce the cell viability of human gingival fibroblasts and periodontal ligament stem cells for a 1 h incubation