Stress resistance and recovery potential of culturable and viable but nonculturable cells of Vibrio vulnificus

Abstract

The estuarine, human-pathogenic bacterium Vibrio vulnificus responds to low temperature by the formation of viable but nonculturable (VBNC) cells, while Starvation a t moderate temperatures allows for maintenance O f culturability of this organism. Recovery of cold-incubated populations of V. vulnificus was restricted to the culturable fraction in slide cultures and most probable number assays. These populations, however, gave between 1.1-and 8-fold higher c.f.u. counts on soft agar plates than on ordinary agar plates, indicating that a small and variable fraction of the cell population was injured rather than nonculturable. Thus, the population of cold-incubated cells is composed of culturable, injured and nonculturable cells, with the numbers of the culturable and injured cells rapidly decreasing during cold incubation. Recovery of nonculturable cells of the organism, however, could not be obtained by any combination of temperature and nutrient shifts in any of the assays. VBNC cells of the organism were assessed with regard to their persistence and stress resistance in comparison to growing and starved cells. The sonication resistance of VBNC cells was initially similar to that of growing cells, but increased during prolonged cold incubation. The final resistance of cold-incubated VBNC cells was equal to the markedly increased resistance of starving cells, which also displayed increased resistance against exposure to ethanol and mechanical stress. Our results indicate that in spite of the apparent absence of recovery under a wide range of laboratory conditions, VBNC cells of V. vulnificus undergo changes at low temperature which potentially allow them to persist for extended periods.

Effect of temperature, salinity and nutrient content on the survival responses of Vibrio splendidus biotype I

“…The defined media were based on those described by Weichart & Kjelleberg (1996), although three different nutrient and salt concentrations were prepared. Nutrients were aseptically added to the microcosms at final concentrations of 17 or 1 g l Nalidixic acid direct counts (NADC) and acridine orange total counts (AOTC).…”

Nutrient-dependent, rapid transition of Vibrio cholerae to coccoid morphology and expression of the toxin co-regulated pilus in this form

“…Decreasing size would enable the coccoid cell to have the greatest surface area for nutrient uptake while maintaining the least amount of cell mass (Baker et al, 1983). In addition, these coccoid cells, as observed in Vibrio vulnificus, have an increased resistance to cold shock, heat shock, sonication, ethanol, and mechanical stress (Weichart & Kjelleberg, 1996), contributing to survival and persistence in the environment. Thus, it has been suggested that the morphological conversion to a coccoid state may be a general survival mechanism of V. cholerae.…”

Morphological Alteration and Survival of Burkholderia pseudomallei in Soil Microcosms

“…Moreover, several studies have reported that VBNC cells had higher physical and chemical resistance than culturable cells. [44][45][46] Our investigation into the fate of B. pseudomallei during a 120-day period in various soil microcosms using the LIVE/ DEAD ® BacLight ™ assay demonstrated both the culturability and viability of a B. pseudomallei environmental isolate grown in a control soil microcosm ( Figure 4A and B). Our results strengthen previous results demonstrating that endemic soils provided environmental niches for the survival of B. pseudomallei.…”