Study On The Function Of KdpD/KdpE And CheA/CheY Two-Component Signal Transduction System In Biotite Weathering Of Rhizobium Pusense S41

Mineral weathering includes physical,chemical and biological weathering.Bacteria play important role in mineral weathering.In this study,a highly efficient mineral-weathered bacterium Rhizobium pusense S41,which its complete genome was sequenced,was selected as the tested strain.It was found that some two-component regulatory systems(TCS)(such as KdpD/KdpE system,CheA/CheY system,etc.)Of strain S41 have significant differential expression.In this study,KdpD/KdpE and the CheA/CheY systems were analyzed by constructing a single mutant strain,and to explore its role in mineral weathering of strain S41.In this study,the effect of KdpD/KdpE system on the process of biotite and potash feldspar weathering by the strain was analyzed by knocking out the KdpE gene.It has been found that the absence of KdpE significantly affects the attachment of strain S41 on different rock surfaces.It was found that there was no difference between the mutant S41?KdpE and wild-type strain on extracellular polysaccharide production,motility,and biofilm formation ability.In addition,it was also found that potassium ion starvation and sodium salt stress affected the weathering ability of strain S41.In order to further explore the impact of the chemotaxis system of strain S41 on the ability to weather biotite,S41?CheA,the loss-of-function mutant of strain S41 chemotaxis system(CheA/CheY system),was constructed by knocking out the CheA gene.In order to further explore the role of the chemotaxis system of strain S41 in biotite weathering,biotite weathering ability was compared between mutant S41?CheA and the wild strain S41.It was found that biotite weathering of the mutant S41?CheA was significantly reduced compared to the wild strain.The concentrations of soluble Fe,Al,Si in the culture medium in the presence of the mutant S41?heA were only 1/3-1/2 of those in the presence of the wild-type strain;exopolysaccharide production was reduced by about 1/3 in the presence of the mutant strain;and the amount of bacteria on the mineral surfaces decreased significantly.At day 5,the amount of biofilm on the biotite surfaces of the mutant strain S41?CheA was less than 1/20 of that in the presence of the wild-strain.In addition,the motility and biofilm formation capacity of the mutant strain S41?CheA were all significantly reduced,suggesting that the chemotaxis system of strain S41 affects its biosorption of the mineral surface by affecting the biofilm and extracellular polysaccharide synthesis capacity,and ultimately has a significant effect on weathering ability of strain S41.RT-PCR analysis showed that the 7 McPs genes were differentially expressed in the mineral weathering process of the strain except McP-02591.It was found that,by capillary method,strain S41 has significant chemotaxis to Fe3+and Mn2+,has a weak chemotaxis to K+;and has no chemotaxis to Zn2+.Moreover,strain S41 was significantly more sensitive to Fe3+than to Mn2+.Furthermore,the chemotaxis of the mutant strain S41?CheA to Fe3+and Mn2+ was significantly weaker than that of the wild-type strain.These results suggested that the chemotaxis of strain S41 to Fe3+ and Mn2+ is regulated by the CheA/CheY system.