Insights into a Pyruvate Sensing and Uptake System in Vibrio campbellii and Its Importance for Virulence

Abstract

Pyruvate is a key metabolite in living cells and has been shown to play a crucial role in the virulence of several bacterial pathogens. The bioluminescent Vibrio campbellii , a severe infectious burden for marine aquaculture, excretes extraordinarily large amounts of pyruvate during growth and rapidly retrieves it by an as-yet unknown mechanism. We have now identified the responsible pyruvate transporter, here named BtsU, and our results show that it is the only pyruvate transporter in V. campbellii . Expression of btsU is tightly regulated by the membrane-integrated LytS-type histidine kinase BtsS, a sensor for extracellular pyruvate, and the LytTR-type response regulator BtsR. Cells lacking either the pyruvate transporter or sensing system show no chemotactic response towards pyruvate, indicating that intracellular pyruvate is required to activate the chemotaxis system. Moreover, pyruvate sensing and uptake were found to be important for the resuscitation of V. campbellii from the viable but nonculturable (VBNC) state and the bacterium’s virulence against brine shrimp larvae. IMPORTANCE Bacterial infections are a serious threat to marine aquaculture, one of the fastest growing food sectors on earth. Therefore, it is extremely important to learn more about the pathogens responsible, one of which is Vibrio campbellii . This study sheds light on the importance of pyruvate sensing and uptake for V. campbellii , and reveals that the bacterium possesses only one pyruvate transporter, which is activated by a pyruvate-responsive histidine kinase/response regulator system. Without the ability to sense or take up pyruvate, the virulence of V. campbellii towards gnotobiotic brine shrimp larvae is strongly reduced.

Identification of two pyruvate transporters inSalmonella entericaserovar Typhimurium and their biological relevance

“…We found a 12-fold upregulation of btsT in the Δ btsT mutant and a 50-fold upregulation in the Δ btsT Δ cstA mutant compared to that in the wild-type (Figure S1C). A similar feedback regulation was observed for btsT in the pathogen Vibrio campbellii (Göing et al, 2021), but the exact mechanism is unknown. In Δ cstA cells, the expression pattern of btsT over time was the same as that in the wild-type (Figure S1C).…”

“…In contrast, the fish pathogen Vibrio campbellii, which excretes extraordinarily high amounts of pyruvate, harbors only one pyruvate sensing system and one transporter (Göing et al, 2021).…”

“…In contrast, the fish pathogen Vibrio campbellii , which excretes extraordinarily high amounts of pyruvate, harbors only one pyruvate sensing system and one transporter (Göing et al, 2021). Moreover, in contrast to pyruvate uptake systems, no exporter of pyruvate is known in any organism.…”

“…These results indicate that pyruvate uptake is necessary for chemotaxis to pyruvate, leading to the conclusion that the chemotactic response must be activated by intracellular pyruvate. Similarly, for other gamma-proteobacteria it was described previously that the deletion of pyruvate transporter gene(s) impairs chemotaxis to pyruvate (Gasperotti et al, 2020;Göing et al, 2021). In E. coli, it has been shown that the phosphotransferase system (PTS) can sense pyruvate inside cells and that signals from the PTS are transmitted linearly to the chemotaxis system (Neumann et al, 2012;Somavanshi et al, 2016).…”

“…The role of pyruvate in the inactivation of ROS is important for the resuscitation of viable but non-culturable (VBNC) bacteria. Pyruvate is required to “wake up” cells from this dormant state and re-enter culturability (Dong et al, 2020; Göing et al, 2021; Mizunoe et al, 1999; Vilhena et al, 2019). S .…”