Viability and Endogenous Substrates Used During Starvation Survival of Rhodospirillum rubrum

Abstract

Cells of Rhodospirillum rubrum were grown photoorganotrophically and chemoorganotrophically and then starved for organic carbon and combined nitrogen under four conditions: anaerobically in the light and dark and aerobically in the light and dark. Illumination prolonged viability and suppressed the net degradation of cell material of phototrophically grown cells, but had no effect on chemotrophically grown cells that did not contain bacteriochlorophyll. The halflife survival times of carbohydrate-rich phototrophically grown cells during starvation anaerobically or aerobically in the light were 17 and 14.5 days, respectively. The values for starvation aerobically and anaerobically in the dark were 3 and 0.5 days, respectively. Chemotrophically grown cells had half-life survival times of 3 and 4 days during starvation aerobically in the light and dark, respectively, and 0.8 day during starvation anaerobically in the light or dark. Of all cell constituents examined, carbohydrate was most extensively degraded during starvation, although the rate of degradation was slowest for phototrophically grown cells starved anaerobically in the light. Phototrophically grown cells containing poly-Bi-hydroxybutyrate as carbon reserve were less able to survive starvation anaerobically in the light than were carbohydrate-rich cells starved under comparable conditions. Light intensity had a significant effect on viability of phototrophically grown cells starving anaerobically. At light intensities of 320 to 650 lx, the halflife survival times were 17 to 24 days. At 2,950 to 10,500 lx, the survival times decreased to 1.5 to 5.5 days. The kinetics of cell death correlated well with the rate of loss of cell mass of starving cells. However, the cause of death could not be attributed to degradation of any specific cell component.Most bacteria are periodically subjected in their natural habitat to periods of starvation stress. Bacteria starving for exogenous energyyielding substrates depend on endogenous metabolism of intracellular substrates to provide the energy required for performing life-sustaining processes such as control of intracellular pH and osmotic pressure, maintenance of selective permeability, and turnover synthesis of macromolecules. This energy, derived from endogenous metabolism for the purpose of survival, is terned energy of maintenance (5,7).The subjects of the response of bacteria to starvation stress and the role of endogenous metabolism in survival have been extensively reviewed (5)(6)(7)15,21,22,31). Usually, specialized cellular reserves such as carbohydrate or poly-,B-hydroxybutyric acid (PHB) are the first substrates for endogenous metabolism. As these are depleted, RNA and sometimes protein are utit Journal article no. 8330 of the Michigan Agricultural Experiment Station.on July 16, 2020 by guest

Increase of Salt Tolerance in Carbon-Starved Cells of Rhodopseudomonas palustris Depending on Photosynthesis or Respiration

“…ATP content significantly increased to (12.9 ± 0.87) × 10 −16 mol CFU −1 and decreased to (4.06 ± 0.45) × 10 −16 mol CFU −1 after 1-d anaerobic starvation in the light and the dark, respectively. As suggested previously [ 23 , 28 ], ATP is probably consumed to maintain viability even under carbon starvation conditions, but in the case of this bacterium ATP can be photosynthetically produced in the light. When aerobic dark conditions were applied after growth termination, the 1-d aerobic starved cells showed high ATP contents, (7.49 ± 0.11) × 10 −16 mol CFU −1 , in contrast to the anaerobic starved cells in the dark.…”

“…Purple photosynthetic bacteria are able to convert light energy to ATP by anoxygenic cyclic photophosphorylation. It has been reported that illumination prolongs the viability of purple photosynthetic bacteria [ 23 , 24 , 25 ]. In addition, 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 ].…”

Influence of growth rate and starvation on fluorescent in situ hybridization of Rhodopseudomonas palustris

“…However, during anaerobic starvation in the presence of light viability was maintained at a relatively high level for a much longer period of time. This is not unexpected in view of the fact that in this organism the presence of light may act as a source of energy for maintenance purposes in the absence of an external growth substrate [46]. The presence of light also resulted in a significantly increased level of total RNA in phototrophically grown cells of R. palustris compared with cells grown aerobically in the dark.…”

Survival and transfer ability of phylogenetically diverse bacterial endosymbionts in environmental Acanthamoeba isolates

“…Although the reason underlying the loss of viability is unknown, these results suggest that the interactions between bacteria and amoebae are stably maintained and that the survival of bacterial endosymbionts are dependent on amoebae, possibly for the acquirement of energy and for protection against environmental stresses. Our phylogenic analysis confirmed that endosymbiont eS31 was most related to Trojanella sp., which belongs to the family Rhodospirillaceae , which are phototrophic bacteria (Breznak et al. , 1978).…”

“…stably maintained and that the survival of bacterial endosymbionts are dependent on amoebae, possibly for the acquirement of energy and for protection against environmental stresses. Our phylogenic analysis confirmed that endosymbiont eS31 was most related to Trojanella sp., which belongs to the family Rhodospirillaceae, which are phototrophic bacteria (Breznak et al, 1978). Unique properties, such as this may be associated with the rapid loss of eS31 viability immediately after being drawn from amoebae.…”