Abstract
BackgroundAn efficient signal transduction system allows a bacterium to sense environmental cues and then to respond positively or negatively to those signals; this process is referred to as taxis. In addition to external cues, the internal metabolic state of any bacterium plays a major role in determining its ability to reside and thrive in its current environment. Similar to external signaling molecules, cytoplasmic signals are also sensed by methyl-accepting chemotaxis proteins (MCPs) via diverse ligand binding domains. Myxobacteria are complex soil-dwelling social microbes that can perform a variety of physiologic and metabolic activities ranging from gliding motility, sporulation, biofilm formation, carotenoid and secondary metabolite biosynthesis, predation, and slime secretion. To live such complex lifestyles, they have evolved efficient signal transduction systems with numerous one- and two-component regulatory system along with a large array of chemosensory systems to perceive and integrate both external and internal cues.ResultsHere we report the in silico characterization of a putative energy taxis cluster, Cc-5, which is present in only one amongst 34 known and sequenced myxobacterial genomes, Corallococcus coralloides. In addition, we propose that this energy taxis cluster is involved in oxygen sensing, suggesting that C. coralloides can sense (either directly or indirectly) and then respond to changing concentrations of molecular oxygen.ConclusionsThis hypothesis is based on the presence of a unique MCP encoded in this gene cluster that contains two different oxygen-binding sensor domains, PAS and globin. In addition, the two monooxygenases encoded in this cluster may contribute to aerobic respiration via ubiquinone biosynthesis, which is part of the cytochrome bc1 complex. Finally, we suggest that this cluster was acquired from Actinobacteria, Gammaproteobacteria or Cyanobacteria. Overall, this in silico study has identified a potentially innovative and evolved mechanism of energy taxis in only one of the myxobacteria, C. coralloides.
Highlights
An efficient signal transduction system allows a bacterium to sense environmental cues and to respond positively or negatively to those signals; this process is referred to as taxis
We scanned 8,075 complete genomes downloaded from National Center for Biotechnology Information (NCBI) and identified PAS domains in almost 90% (7,226) of the genomes; many are associated with regulatory domains such as HisKA, HATPase_c, Response_reg, HTH, MCPsignal, etc
The MCPsignal domain is most frequently associated with HAMP domains, and several other ligand binding Pfam domains such as 4HB_MCP_1, dCache_1, TarH, PAS_3, sCache_2, PAS_9, CZB, HBM, Protoglobin, PAS_4, Cache_3-Cache_2, PilJ, CHASE3, etc., supporting the previous findings [12]
Summary
An efficient signal transduction system allows a bacterium to sense environmental cues and to respond positively or negatively to those signals; this process is referred to as taxis. Myxobacteria are complex soil-dwelling social microbes that can perform a variety of physiologic and metabolic activities ranging from gliding motility, sporulation, biofilm formation, carotenoid and secondary metabolite biosynthesis, predation, and slime secretion To live such complex lifestyles, they have evolved efficient signal transduction systems with numerous one- and two-component regulatory system along with a large array of chemosensory systems to perceive and integrate both external and internal cues. Bacteria actively sense their rapidly changing environment and alter their behavior in response.
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