Impact of hypoxia on gene expression patterns by the human pathogen, Vibrio vulnificus, and bacterial community composition in a North Carolina estuary

Abstract

Estuarine environments are continuously being shaped by both natural and anthropogenic sources which directly/indirectly influence the organisms that inhabit these important niches on both individual and community levels. Human infections caused by pathogenic Vibrio species are continuing to rise, and factors associated with global climate change have been suggested to be impacting their abundance and geographical range. Along with temperature, hypoxia has also increased dramatically in the last 40 years, which has led to persistent dead zones worldwide in areas where these infections are increasing. Thus, utilizing membrane diffusion chambers, we investigated the impact of in situ hypoxia on the gene expression of one such bacterium, Vibrio vulnificus, which is an inhabitant of these vulnerable areas worldwide. By coupling these data with multiple abiotic factors, we were able to demonstrate that genes involved in numerous functions, including those involved in virulence, environmental persistence, and stressosome production, were negatively correlated with dissolved oxygen. Furthermore, comparing 16S ribosomal RNA, we found similar overall community compositions during both hypoxia and normoxia. However, unweighted beta diversity analyses revealed that although certain classes of bacteria dominate in both low‐ and high‐oxygen environments, there is the potential for quantitative shifts in lower abundant species, which may be important for effective risk assessment in areas that are becoming increasingly more hypoxic. This study emphasizes the importance of investigating hypoxia as a trigger for gene expression changes by marine Vibrio species and highlights the need for more in depth community analyses during estuarine hypoxia.

The Vibrio vulnificus stressosome is an oxygen-sensor involved in regulating iron metabolism

“…Whole genome sequencing has shown that the stressosome gene cluster is particularly well conserved in clinical V. vulnificus isolates (Biotype 1) and less frequently found in environmental strains (Biotype 2), suggesting that the stressosome may play a role during infection 24 , 26 . Furthermore, the rsbRSTX locus is transcribed during periods of reduced oxygen availability in sea water, showing that the stressosome operon is active in the natural habitat of this pathogen 27 . The rsbRSTX gene cluster is also conserved in other important pathogenic Vibrio species including Vibrio coralliilyticus , causing global coral bleaching 28 , Vibrio nigripulchritudo , an emerging pathogen of farmed shrimp 29 , and Vibrio brasiliensis 30 that was isolated from a marine aquaculture environment 31 .…”

The Vibrio vulnificus stressosome is dispensable in nutrient-rich media

“… V. vulnificus experiences variation in O 2 levels both in the environment and in the human host [27]. Moreover, the V.…”

TheVibrio vulnificusstressosome is dispensable in nutrient-replete conditions

“…Next, growth characterisation of the two strains was performed in LBN at 30°C and 37°C, in aerobic and O 2 -depleted conditions. V. vulnificus experiences variation in O 2 levels both in the environment and in the human host (25). Moreover, the V. brasiliensis stressosome has been shown to bind O 2 in vitro (26).…”

“…The first formed by the genes encoding for the three stressosome proteins VvrsbR, VvrsbS, VvrsbT (RsbR, RsbS and RsbT in B. subtilis ) and the phosphatase VvrsbX (RsbX) and the latter encoding for a putative regulatory output of the stressosome, a two-component system (TCS) most likely involved in c-di-GMP hydrolysis (22). This locus has been identified in approximately 50% of the sequenced strains and its expression has been proved both in nature and laboratory conditions (23–25). Moreover, the heme-binding globin domain at the N-terminal of VvuR and the biochemical characterisation of these proteins from V. brasiliensis has shown a potential role in surviving or tolerating anaerobic conditions (26).…”