Bacteria play important roles in mineral weathering and soil formation. However, few reports of mineral weathering bacteria inhabiting subsurfaces of soil profiles have been published, raising the question of whether the subsurface weathering bacteria are fundamentally distinct from those in surface communities. To address this question, we isolated and characterized mineral weathering bacteria from two contrasting soil profiles with respect to their role in the weathering pattern evolution, their place in the community structure, and their depth-related changes in these two soil profiles. The effectiveness and pattern of bacterial mineral weathering were different in the two profiles and among the horizons within the respective profiles. The abundance of highly effective mineral weathering bacteria in the Changshu profile was significantly greater in the deepest horizon than in the upper horizons, whereas in the Yanting profile it was significantly greater in the upper horizons than in the deeper horizons. Most of the mineral weathering bacteria from the upper horizons of the Changshu profile and from the deeper horizons of the Yanting profile significantly acidified the culture media in the mineral weathering process. The proportion of siderophore-producing bacteria in the Changshu profile was similar in all horizons except in the Bg2 horizon, whereas the proportion of siderophore-producing bacteria in the Yanting profile was higher in the upper horizons than in the deeper horizons. Both profiles existed in different highly depth-specific culturable mineral weathering community structures. The depth-related changes in culturable weathering communities were primarily attributable to minor bacterial groups rather than to a change in the major population structure.

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Rock-weathering bacteria from the surfaces of less and more altered tuffs were isolated and characterized, along with the adjacent soils, with respect to their rock weathering pattern, stress resistance, community structure, and the changes in the rocks and soils.

A novel type of rock-weathering bacterium was isolated from weathered rock (tuff) surface collected from Dongxiang (Jiangxi, eastern China). Cells of strain G19T were Gram-reactionpositive, rod-shaped, endospore-forming and non-motile. The strain was aerobic, catalase-and oxidase-positive, and grew optimally at 30 6C and pH 7. were plated onto agar plates to determine total culturable bacteria. The plates were incubated for 3 days at 28 u C. Strain G19T was picked and able to weather tuff. Rock dissolution experiments showed that the amounts of Si, Al and Fe released from the tuff by strain G19 T were 2.5-fold, 92-fold and 130.4-fold greater than the uninoculated controls, respectively. The strain was routinely cultured on R2A agar medium 0.5 g yeast extract, 0.5 g proteose peptone No. 3, 0.5 g casamino acids, 0.5 g glucose, 0.5 g soluble starch, 0.3 g sodium pyruvate, 0.3 g K 2 HPO 4 , 0.05 g MgSO 4 .7H 2 O, 15 g agar for additional taxonomic experiments. The strain was maintained as a glycerol suspension (40 %, v/v) at 280 u C.In order to characterize strain G19 T , standard phenotypic tests were selected according to the recommended Minimal Abbreviations: DPG, diphosphatidylglycerol; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; PLS, unidentified lipid.

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