In this study, the mineral-weathering bacterium Pseudomonas azotoformans F77, isolated from the soil of a debris flow area, was evaluated for its weathering activity under direct contact with biotite or without contact. Then, biotite-weathering behaviors of strain F77, its mutants that were created by deleting the gcd and adh genes, which are involved in gluconic acid metabolism and pilus formation, respectively and the double mutant F77gcdadh, were compared. The relative gene expression levels of F77 and its mutants F77gcd and F77adh were also analyzed in the presence of biotite. Direct contact with biotite increased Fe and Al release from the mineral in the presence of F77. All strains had a similar ability to release Fe and Al from the mineral except for F77gcd and F77adh. Mobilized Fe and Al concentrations were decreased by up to 72, 26, and 87% in the presence of F77gcd, F77adh, and F77gcdadh, respectively, compared to those observed in the presence of F77 during the mineral-weathering process. Gluconic acid production was decreased for F77gcd and F77gcdadh, while decreased cell attachment on the mineral surface was observed for F77adh compared to that observed for F77. The F77 genes involved in pilus formation and gluconic acid metabolism showed increased expression levels in the presence of biotite. The results of this study showed the important role of the genes involved in gluconic acid metabolism and pilus formation in mineral weathering by F77 and demonstrated the distinctive effect of these genes on mineral weathering by F77.

IMPORTANCE Bacteria play an important role in mineral weathering and soil formation; although the molecular mechanisms underlying the interactions between bacteria and silicate minerals are poorly understood. In this study, the interactions between biotite and the highly effective mineral-weathering bacterium P. azotoformans F77 were characterized. Our results showed that the genes involved in gluconic acid metabolism and pilus formation play important roles in mineral weathering by F77. The presence of biotite could promote the expression of these genes in F77, and a distinctive effect of these genes on mineral weathering by F77 was observed in this study. Our results provide new knowledge and promote better understanding regarding the interaction between silicate minerals and mineral-weathering bacteria and of the molecular mechanisms involved in these processes.

在这项研究中，评估了从泥石流区域土壤中分离出的矿物风化细菌偶氮假单胞菌F77在直接接触黑云母或不接触黑云母的情况下的风化活性。然后，比较了菌株F77的黑云母风化行为，该突变体是通过删除分别参与葡萄糖酸代谢和菌毛形成的gcd和adh基因而产生的，并且还突变了F77 gcd adh的双突变体。F77及其突变体F77 gcd和F77 adh的相对基因表达水平在黑云母存在下也进行了分析。在F77存在下，与黑云母的直接接触增加了铁和铝从矿物中的释放。除F77 gcd和F77 adh外，所有菌株都有从矿物中释放铁和铝的类似能力。与矿物风化过程中存在F77的情况相比，在存在F77 gcd，F77 adh和F77 gcd adh的情况下，动员的Fe和Al浓度分别降低多达72％，26％和87％。葡糖酸产量为F77降低GCD和F77 GCD ADH，而观察到F77在矿物表面上降低的细胞附着ADH与观察到的F77相比。在黑云母存在下，参与菌毛形成和葡萄糖酸代谢的F77基因显示出增加的表达水平。这项研究的结果表明，参与葡萄糖酸代谢和菌毛形成的基因在F77矿物风化中的重要作用，并证明了这些基因对F77矿物风化的独特作用。

重要信息细菌在矿物风化和土壤形成中起着重要作用。尽管对细菌和硅酸盐矿物之间相互作用的分子机制了解甚少。在这项研究中，黑云母与高效矿物风化细菌偶氮假单胞菌之间的相互作用F77被表征。我们的结果表明，参与葡萄糖酸代谢和菌毛形成的基因在F77矿物风化中起重要作用。黑云母的存在可以促进这些基因在F77中的表达，并且在这项研究中观察到这些基因对F77矿物风化的独特作用。我们的结果为硅酸盐矿物与矿物风化细菌之间的相互作用以及这些过程中涉及的分子机理提供了新的知识，并促进了人们对它们的更好的理解。