AUTHOR=Luo Zhen , Yue Shan , Chen Ti , She Pengfei , Wu Yuan , Wu Yong 

TITLE=Reduced Growth of Staphylococcus aureus Under High Glucose Conditions Is Associated With Decreased Pentaglycine Expression

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.537290

DOI=10.3389/fmicb.2020.537290

ISSN=1664-302X

ABSTRACT=<p>The high-glucose-induced cytotoxicity in diabetes has been widely recognized. <italic>Staphylococcus aureus</italic> is the most frequent pathogen isolated from diabetic foot ulcers, but the properties of this bacterium under high glucose conditions remain unclear. <italic>S. aureus</italic> grew in medium usually forms weak biofilm, and which was significantly increased by addition of glucose. However, extracellular DNA (eDNA), an important component of biofilms, was markedly decreased in presence of 15 mM glucose. The reduced eDNA content was not caused by degradation, because the nuclease activity of biofilm supernatants with glucose was significantly decreased due to the acidic pH of the medium. Under planktonic state, the growth of <italic>S. aureus</italic> was significantly decreased in the Luria-Bertani (LB) medium supplemented with 25 mM glucose, and the reduced growth of <italic>S. aureus</italic> by glucose was dose-dependent. Except for glucose, the growth of planktonic <italic>S. aureus</italic> was also markedly decreased by fructose or sucrose. Amounts of acid metabolites were produced under high glucose conditions, but the survival of planktonic <italic>S. aureus</italic> was unaffected by these acidic conditions. Cells of <italic>S. aureus</italic> from the culture medium with glucose had a thinner cell wall and highly resistant to lysostaphin compared with the bacteria cultured in LB medium. mRNA expression of genes encoding pentaglycine bridges, the substrate of lysostaphin, was significantly decreased in <italic>S. aureus</italic> by glucose. In addition to <italic>S. aureus</italic>, the growth of <italic>Staphylococcus haemolyticus</italic> and <italic>Staphylococcus epidermidis</italic> was also significantly decreased by an excess of glucose, but strains of <italic>Enterococcus faecalis</italic>, <italic>Escherichia coli</italic>, and <italic>Pseudomonas aeruginosa</italic> were unaffected by glucose. In conclusion, the reduced growth of <italic>S. aureus</italic> under high glucose conditions is due to impairment of the unique cell-wall structure, pentaglycine bridges.</p>