subtilin and epidermin

Cell-density-dependent gene expression appears to be widely spread in bacteria. This quorum-sensing phenomenon has been well established in Gram-negative bacteria, where N-acyl homoserine lactones are the diffusible communication molecules that modulate cell-density-dependent phenotypes. Similarly, a variety of processes are known to be regulated in a cell-density- or growth-phase-dependent manner in Gram-positive bacteria. Examples of such quorum-sensing modes in Gram-positive bacteria are the development of genetic competence in Bacillus subtilis and Streptococcus pneumoniae, the virulence response in Staphylococcus aureus, and the production of antimicrobial peptides by several species of Gram-positive bacteria including lactic acid bacteria. Cell-density-dependent regulatory modes in these systems appear to follow a common theme, in which the signal molecule is a post-translationally processed peptide that is secreted by a dedicated ATP-binding-cassette exporter. This secreted peptide pheromone functions as the input signal for a specific sensor component of a two-component signal-transduction system. Moreover, genetic linkage of the common elements involved results in autoregulation of peptide-pheromone production.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Bacterial Proteins; Bacteriocins; Gram-Positive Bacteria; Molecular Sequence Data; Nisin; Peptides; Pheromones; Signal Transduction; Virulence

Lantibiotics are defined as peptide antibiotics containing the unusual amino acids mesolanthionine, 3-methyllanthionine, dehydroalanine, and dehydrobutyrine. They are synthesized by some gram-positive bacteria. Their inhibitory effect on certain other gram-positive bacteria is explained by detergent-like damage of cytoplasmic membranes. Prominent members of the lantibiotics are nisin of Lactococcus lactis, which can be used as a food preservative, subtilin of Bacillus subtilis, which is similar to nisin, and epidermin of Staphylococcus epidermidis, which is considered in the treatment of acne. Lantibiotics are ribosomally synthesized as prepeptides, which are posttranslationally modified. Genes probably encoding these biosynthetic enzymes and regulatory factors have been identified adjacent to the structural genes of the lantibiotics subtilin, nisin, and epidermin.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Bacillus subtilis; Bacteria; Bacterial Proteins; Bacteriocins; Genes, Bacterial; Lactococcus lactis; Molecular Sequence Data; Nisin; Peptides; Peptides, Cyclic; Protein Conformation; Ribosomes; Staphylococcus epidermidis

Bacillus thuringiensis promotes the growth of numerous economically important crops. The present study presents the complete genome sequence for a mega plasmid present in the type strain of B. thuringiensis ATCC 10792, a typical spore-forming Gram-positive bacterium with insecticidal activity, and investigates its genetic characteristics. The genome was sequenced and assembled de novo using Pac-Bio sequencers and the Hierarchical Genome Assembly Process, respectively. Further genome annotation was performed, and a total of 489 proteins and a novel mega-plasmid (poh1) with 584,623 bps were identified. The organization of poh1 revealed the genes involved in the insecticidal toxin pathway. The genes responsible for antimicrobial, insecticidal and antibiotic activities were well conserved in poh1, indicating an intimate association with plant hosts. The poh1 plasmid contains the gene encoding a novel crystal protein kinase responsible for production of zeta toxin, which poisons insects and other Gram-negative bacteria through the global inhibition of peptidoglycan synthesis. Lantibiotics are a group of bacteriocins that include the biologically active antimicrobial peptide Paenibacillin. Further, poh1 also contains the genes that encode the gramicidin S prototypical antibiotic peptide and tetracycline resistance protein. In conclusion, the strain-specific genes of B. thuringiensis strain ATCC 10792 were identified through complete genome sequencing and bioinformatics data based on major pathogenic factors that contribute to further studies of the pathogenic mechanism and phenotype analyses.

Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Bacillus thuringiensis; Bacteria; Bacterial Toxins; Bacteriocins; Base Sequence; Computational Biology; DNA, Bacterial; Drug Resistance, Microbial; Genome, Bacterial; Insecta; Insecticides; Microbial Sensitivity Tests; Molecular Sequence Annotation; Nisin; Peptides; Plasmids; Protein Kinases; Pyrazines; Tetracycline Resistance; Whole Genome Sequencing

The information responsible for biosynthesis of the lantibiotic subtilin is organized in an operon-like structure that starts with the spaB gene. The spaB gene encodes an open reading frame consisting of 1,030 amino acid residues, and it was calculated that a protein having a theoretical molecular mass of 120.5 kDa could be produced from this gene. This is consistent with the apparent molecular weight for SpaB of 115,000 which was estimated after sodium dodecyl sulfate-gel electrophoresis and identification with SpaB-specific antibodies. The SpaB protein is very similar to proteins EpiB and NisB, which were identified previously as being involved in epidermin and nisin biosynthesis. Upstream from SpaB a characteristic sigma A promoter sequence was identified. An immunoblot analysis revealed that SpaB expression was strongly regulated. No SpaB protein was detected in the early logarithmic growth phase, and maximum SpaB expression was observed in the early stationary growth phase. The expression of SpaB was strongly correlated with subtilin biosynthesis. Deletion mutations in either of two recently identified regulatory genes, spaR and spaK, which act as a "two-component" regulatory system necessary for growth phase-dependent induction of subtilin biosynthesis (C. Klein, C. Kaletta, and K. D. Entian, Appl. Environ. Microbiol. 59:296-303, 1993), also resulted in failure of SpaB expression. To investigate the intracellular localization of SpaB, vesicles of Bacillus subtilis were prepared. The SpaB protein cosedimented with the vesicle fraction and was released only after vigorous resuspension of the vesicles. Our results suggest that SpaB is membrane associated and that subtilin biosynthesis occurs at the cytoplasmic membrane of B. subtilis.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Antigens, Bacterial; Bacillus subtilis; Bacterial Proteins; Bacteriocins; Base Sequence; DNA, Bacterial; Genes, Bacterial; Membrane Proteins; Molecular Sequence Data; Nisin; Open Reading Frames; Peptides; Peptides, Cyclic; Sequence Homology, Amino Acid