Abstract
A number of Vibrio spp. belong to the well-studied model organisms used to understand the strategies developed by marine bacteria to cope with adverse conditions (starvation, suboptimal temperature, solar radiation, etc.) in their natural environments. Temperature and nutrient availability are considered to be the key factors that influence Vibrio harveyi physiology, morphology, and persistence in aquatic systems. In contrast to the well-studied effects of temperature and starvation on Vibrio survival, little is known about the impact of visible light able to cause photooxidative stress. Here we employ V. harveyi ATCC 14126T as a model organism to analyze and compare the survival patterns and changes in the protein composition of its cell envelope during the long-term permanence of this bacterium in seawater microcosm at 20 °C in the presence and absence of illumination with visible light. We found that V. harveyi exposure to visible light reduces cell culturability likely inducing the entry into the Viable but Non Culturable state (VBNC), whereas populations maintained in darkness remained culturable for at least 21 days. Despite these differences, the starved cells in both populations underwent morphological changes by reducing their size. Moreover, further proteomic analysis revealed a number of changes in the composition of cell envelope potentially accountable for the different adaptation pattern manifested in the absence and presence of visible light.
Highlights
Vibrio species are frequently used as models organisms to study the strategies developed by marine bacteria to cope with adverse and changing environments
A large number of studies have demonstrated that the survival of vibrios in the natural environment is largely determined by temperature, and some authors [1,2] have indicated that these bacteria represent an important and tangible barometer sensing the impact of climate change in marine ecosystems
These phenotypical changes led to the appearance of cells with the coccoid-like morphology associated with the Viable But Non Culturable (VBNC) state in Vibrio species [39]
Summary
Vibrio species are frequently used as models organisms to study the strategies developed by marine bacteria to cope with adverse and changing environments. Unlike low temperatures (below 13 ◦ C) that could often lead to vibrio’s dormancy and promote acquisition of the Viable But Non Culturable (VBNC) state in Vibrio alginolyticus [3], V. cholerae [4], V. harveyi [5,6], V. parahaemolyticus [7,8], or V. vulnificus [9], moderate temperatures (13 ◦ C to 22 ◦ C) seem to increase the capacity of vibrios to survive under starvation [10,11], thereby potentially increasing the spread of Vibrio species-associated diseases [12,13,14] These effects are more profound during the summer seasons, which are characterized by more intensive solar radiation. Several studies have reported the complex responses of aquatic bacteria exposed to photosynthetically active radiation (PAR; visible light) (400 to 700 nm). While it positively affects the physiology of autochthonous marine
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