Tetrathionate (H2S4O6) is a sulphurated compound abundant in the intestine of aquatic and terrestrial animals during inflammatory processes. Some pathogenic bacterial species have a complex of reductase that lets them use the compound as an alternative acceptor electron in anaerobic conditions, enhancing its growth in anoxic conditions even in carbon source starvation. A genomic survey recently revealed that the marine bacterium Vibrio parahaemolyticus has a genetic locus putatively related to anaerobic reductases of tetrathionate (Fig. 1), however there is no information about its functionality in the species. Thus, this work focuses on testing the effect of tetrathionate on the growth of V. parahaemolyticus and exploring the molecular changes that the species experience by transcriptomic tools.
V. parahaemolyticus CAIM1400 serotype O3:K6 strain was cultured in M9 + 0.3% glucose medium with and with our tetrathionate of potassium (K2S4O6) at 3, 5, 10 and 20 mM in anaerobic conditions. The bacteria growth was monitored during 24 hours by optical density. The cells of the cultures without and with 5 mM K2S4O6 were harvested when they reached approximately 0.6 ODs. The RNA extraction was done with RNeasy Plus Micro kit (Qiagen). The RNAseq library synthesis was done with Stranded Total RNA (Illumina), and sequencing was carried out in a miniseq illumina platform. The processing and analysis of transcriptomic sequences was done with Trimommatic (v0.32), Bowtie software (v.2.3.5.1), FADU (v1.8.3), DESeq2 (v1.40.2) and fgsea (version 1.26.0) of Bioconductor package in R studio.
Tetrathionate improves the growth of V. parahaemolyticus in anaerobic environments with low carbon source availability (Fig. 2). A total of 854 differential expressed genes between the cultures of V. parahaemolyticus without and with tetrathionate 5 Mm, 456 upregulated and 398 down-regulated (Fig. 3). The main molecular pathways altered are related to nutrients transport, ATP hydrolysis activity, oxidoreductases, transcriptional regulators and flagellum components (Fig. 4).