Cell Wall Chemical Composition of Enterococcus faecalis in the Viable but Nonculturable State

Abstract

The viable but nonculturable (VBNC) state is a survival mechanism adopted by many bacteria (including those of medical interest) when exposed to adverse environmental conditions. In this state bacteria lose the ability to grow in bacteriological media but maintain viability and pathogenicity and sometimes are able to revert to regular division upon restoration of normal growth conditions. The aim of this work was to analyze the biochemical composition of the cell wall of Enterococcus faecalis in the VBNC state in comparison with exponentially growing and stationary cells. VBNC enterococcal cells appeared as slightly elongated and were endowed with a wall more resistant to mechanical disruption than dividing cells. Analysis of the peptidoglycan chemical composition showed an increase in total cross-linking, which rose from 39% in growing cells to 48% in VBNC cells. This increase was detected in oligomers of a higher order than dimers, such as trimers (24% increase), tetramers (37% increase), pentamers (65% increase), and higher oligomers (95% increase). Changes were also observed in penicillin binding proteins (PBPs), the enzymes involved in the terminal stages of peptidoglycan assembly, with PBPs 5 and 1 being prevalent, and in autolytic enzymes, with a threefold increase in the activity of latent muramidase-1 in E. faecalis in the VBNC state. Accessory wall polymers such as teichoic acid and lipoteichoic acid proved unchanged and doubled in quantity, respectively, in VBNC cells in comparison to dividing cells. It is suggested that all these changes in the cell wall of VBNC enterococci are specific to this particular physiological state. This may provide indirect confirmation of the viability of these cells.

Long-term survival and the viable but nonculturable state as part of the life cycle of Listonella pelagia

“…damselae (Fouz et al 1998). However, the increase in biovolume found for VBNC cells of Listonella pelagia cultured in a 16 ‰ medium, and the spheroid morphology, would suggest that although membrane activity is maintained, the cells are under osmotic stress implying an alteration of the cell wall, as reported by Signoretto et al (2000). Yet in our case it should be pointed out that changes in cell shape and size could not be related to changes in the membrane protein profiles.…”

Influence of activated charcoal, porcine gastric mucin and β-cyclodextrin on the morphology and growth of intestinal and gastric Helicobacter spp.

“…In general, a spiral to coccoid conversion was more rapid in broth than on solid media, most likely due to the dissolved toxic substances enhancing the coccoid transformation (Moran & Upton, 1987b ;Coudron & Statton, 1995). The ability to delay the spiral to coccoid conversion may be beneficial in the production of cell surface antigens for immunodiagnostic tests since such conversion has been shown to induce changes in the cell wall composition of H. pylori and other bacteria (Costa et al, 1999 ;Signoretto et al, 2000).…”

A dormancy state in nonspore-forming bacteria

“…1d, 2d, and 3d). In an earlier study, it was shown that there were modifications in the peptidoglycan of the bacterial cell wall of these dormant cells (Signoretto et al 2003). Subsequently, it was suggested that peptidoglycon hydrolysis driven by the antidormancy factor (also called as resuscitation promoting factor) is a key in vivo step in the revitalization of dormant cells, resulting in cell division (Mukamolova et al 1998; review by Keep et al 2006 and references therein).…”