The sulfur/sulfonates transport systems in Xanthomonas citri pv. citri

Abstract

BackgroundThe Xanthomonas citri pv. citri (X. citri) is a phytopathogenic bacterium that infects different species of citrus plants where it causes canker disease. The adaptation to different habitats is related to the ability of the cells to metabolize and to assimilate diverse compounds, including sulfur, an essential element for all organisms. In Escherichia coli, the necessary sulfur can be obtained by a set of proteins whose genes belong to the cys regulon. Although the cys regulon proteins and their importance have been described in many other bacteria, there are no data related to these proteins in X. citri or in the Xanthomonas genus. The study of the relevance of these systems in these phytopathogenic bacteria that have distinct mechanisms of infection is one essential step toward understanding their physiology. In this work, we used bioinformatics, molecular modeling and transcription analysis (RT-PCR) to identify and characterize the putative cys regulon genes in X. citri.ResultsWe showed that the ATP Binding Cassette Transporter (ABC transporter) SbpCysUWA for sulfate uptake is conserved in X. citri and translated in presence of sulfate. On the other hand, differently from what is predicted in databases, according molecular modeling and phylogenetic analysis, X. citri does not show a proper taurine transporter, but two different ABC systems related to the alkanesulfonate/sulfonate transport that were recently acquired during evolution. RT-PCR analysis evidenced that these genes and their putative transcriptional regulator CysB are rather transcripted in XAM1, a medium with defined concentration of sulfate, than LB.ConclusionsThe presence of at least three distinct systems for sulfate and sulfonates assimilation in X. citri evidenced the importance of these compounds for the bacterium. The transcription of genes involved with alkanesulfonate/sulfur compounds in XAM1 along to CysB suggests that despite the differences in the transporters, the regulation of these systems might be similar to the described for E. coli. Altogether, these results will serve as a foundation for further studies aimed to understanding the relevance of sulfur in growth, virulence and pathogenesis of X. citri and related bacteria.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1736-5) contains supplementary material, which is available to authorized users.

The periplasmic binding protein NrtT affects xantham gum production and pathogenesis in Xanthomonas citri

“…The comparison of NrtT with putative orthologues using the BLASTP tool confirmed similarities with nitratebinding proteins from different species of the genus Xanthomonas and the two alkanesulfonate-binding proteins from X. citri, SsuA1 and SsuA2 [17]. Moreover, the same genome organization found in X. citri is present in Xanthomonas campestris, another important phytopathogen that infects citrus plants but with a different mechanism (Fig.…”

“…Furthermore, from the list of importers, 14 genes are related to the uptake of nitrate/taurine or sulfate/aliphatic sulfonates and akanesulfonates, showing that these compounds might confer on the bacterium some advantage during its growth and evidencing the relevance of sulfur in this process. In fact, during growth of the bacterium in LB broth and XAM1 media, the ABC transporters responsible for sulfate uptake (SbpCysUWA) and the additional systems related to the transport of alkanesulfonates and/or organosulfur compounds (SsuABC1 and SsuABC2) are differentially induced [17], suggesting a regulation based on sulfur availability. Studies have shown a significant and continuous activation of the sbpcysUWA promoter during the first stages of infection of X. citri in C. sinensis leaves, indicating the need for sulfate in these conditions [18].…”

Unusual Sulfur Requirements During Laboratory Growth ofLuteibacter

“…At a minimum, sulfur is required for growth of all known bacteria under all known conditions because it is a main component of an amino acid (methionine) present in all translated proteins (1) . Sulfate is one of the most widely available and utilized sulfur sources for terrestrial bacteria, which is highlighted by conservation of the sulfate transport pathway genes cysAUWP across many proteobacterial strains including xanthomonads (10) . That certain clades of Luteibacter have altered abilities to metabolize sulfate compared to closely related outgroups like Xanthomonas , speaks to a difference in ecological niche for these strains compared to their more widely studied relatives.…”

Responses of Acidithiobacillus thiooxidans A01 to Individual and Joint Nickel (Ni2+) and Ferric (Fe3+)

“…It is worth noting that cysA, cysB and serineO were upregulated in the presence of Ni 2+ and Fe 3+ . Sulfate/thiosulfate import ATP-binding protein (cysA) and transport sulfate as a sulfur source for cysteine biosynthesis [34]. Moreover, serine O-acetyltransferase (serine O) catalyze the reaction: L-serine + acetyl-coenzyme A ⇆ O-acetyl-L-serine + coenzyme A [35], subsequently, the O-acetyl-L-serine can be converted into organic sulfur molecules cysteine [36].…”