Abstract
The Gram-positive bacterium Staphylococcus carnosus (S. carnosus) TM300 is an apathogenic staphylococcal species commonly used in meat starter cultures. As with all Gram-positive bacteria, its cytoplasmic membrane is surrounded by a thick peptidoglycan (PGN) or murein sacculus consisting of several layers of glycan strands cross-linked by peptides. In contrast to pathogenic staphylococci, mainly Staphylococcus aureus (S. aureus), the chemical composition of S. carnosus PGN is not well studied so far. UPLC/MS analysis of enzymatically digested S. carnosus TM300 PGN revealed substantial differences in its composition compared to the known pattern of S. aureus. While in S. aureus the uncross-linked stem peptide consists of a pentapeptide, in S. carnosus, this part of the PGN is shortened to tripeptides. Furthermore, we found the PGN composition to vary when cells were incubated under certain conditions. The collective overproduction of HlyD, FtsE and FtsX—a putative protein complex interacting with penicillin-binding protein 2 (PBP2)—caused the reappearance of classical penta stem peptides. In addition, under high sugar conditions, tetra stem peptides occur due to overflow metabolism. This indicates that S. carnosus TM300 cells adapt to various conditions by modification of their PGN.
Highlights
Staphylococcus carnosus (S. carnosus, S. c.) TM300 is an apathogenic, coagulase-negative,“food grade” staphylococcal species [1] commonly used as meat starter culture for raw sausages [2].Its 2.56 Mbp genome has the highest GC content of all staphylococcal species sequenced so far.While virulence and toxicity factors are almost completely missing from the genome, most of the metabolic pathways are present
The whole muropeptide pattern of S. carnosus was shifted to shorter retention times compared to S. aureus
We could show that the PGN of the apathogenic bacterium S. carnosus TM300 differs from the well-studied PGN of the pathogen S. aureus
Summary
Staphylococcus carnosus (S. carnosus, S. c.) TM300 is an apathogenic, coagulase-negative,“food grade” staphylococcal species [1] commonly used as meat starter culture for raw sausages [2].Its 2.56 Mbp genome has the highest GC content of all staphylococcal species sequenced so far.While virulence and toxicity factors are almost completely missing from the genome, most of the metabolic pathways are present. Staphylococcus carnosus (S. carnosus, S. c.) TM300 is an apathogenic, coagulase-negative,. “food grade” staphylococcal species [1] commonly used as meat starter culture for raw sausages [2]. Its 2.56 Mbp genome has the highest GC content of all staphylococcal species sequenced so far. While virulence and toxicity factors are almost completely missing from the genome, most of the metabolic pathways are present. As typical for starter cultures, it harbors various sugar degradation pathways [3,4]. The general features of the peptidoglycan (PGN) of S. carnosus TM300 are already known. Like Staphylococcus aureus (S. aureus, S. a.) it belongs to the A3α-type with a penta glycine interpeptide bridge [1,5]. N-acetylmuramic acid (MurNAc) residues in the glycan backbone are Antibiotics 2016, 5, 33; doi:10.3390/antibiotics5040033 www.mdpi.com/journal/antibiotics
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