Abstract
Bacteria in natural environments are frequently exposed to nutrient starvation and survive against environmental stresses under non-growing conditions. In order to determine the energetic influence on survivability during starvation, changes in salt tolerance were investigated using the purple photosynthetic bacterium Rhodopseudomonas palustris after carbon starvation under photosynthetic conditions in comparison with anaerobic and aerobic dark conditions. Tolerance to a treatment with high concentration of salt (2.5 M NaCl for 1 h) was largely increased after starvation under anaerobically light and aerobically dark conditions. The starved cells under the conditions of photosynthesis or aerobic respiration contained high levels of cellular ATP, but starvation under the anaerobic dark conditions resulted in a decrease of cellular ATP contents. To observe the large increase of the salt tolerance, incubation of starved cells for more than 18 h under illumination was needed. These results suggest that the ATP-dependent rearrangement of cells induced salt tolerance.
Highlights
Bacteria are often exposed to nutrient-depleted conditions in natural environments [1]
Kanno et al previously examined ATP contents in purple photosynthetic bacteria, Rhodopseudomonas palustris and Rhodospirillum rubrum, under carbon-starved conditions and reported that illumination largely affected the maintenance of cellular ATP contents under carbon-starved conditions [24]. These results suggest that cellular ATP is utilized to increase the survivability of the purple photosynthetic bacteria
Microorganisms 2018, 6, 4 of the purple photosynthetic bacterium R. palustris, which is widely distributed and metabolically versatile [26], and we investigated changes in salt tolerance after short-term starvation under photosynthetic conditions, as compared with anaerobic and aerobic dark conditions
Summary
Bacteria are often exposed to nutrient-depleted conditions in natural environments [1]. Bacterial functions and strategies for survival and distribution in nature are strongly related to nutrientdepleted conditions. Bacteria likely change their cellular metabolisms to adapt to nutrient-depleted conditions [2]. As a pronounced cellular response to nutrient starvation, a cell size reduction has been observed [10,11,12,13,14,15,16,17]. Transcriptional factors responding to the starvation have been extensively examined [19,20,21,22]. It is still unclear how cellular energy contributes to these starvation responses
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