Elucidating complex interactions between bacteria and fungi that determine microbial community structure, composition, and functions in soil, as well as regulate carbon (C) and nutrient fluxes, is crucial to understand biogeochemical cycles. Among the various interactions, competition for resources is the main factor determining the adaptation and niche differentiation between these two big microbial groups in soil. This is because C and energy limitations for microbial growth are a rule rather than an exception. Here, we review the C and energy demands of bacteria and fungi – the two major kingdoms in soil – the mechanisms of their competition for these and other resources, leading to niche differentiation, and the global change impacts on this competition. The normalized microbial utilization preference showed that bacteria are 1.4–5 times more efficient in the uptake of simple organic compounds as substrates, whereas fungi are 1.1–4.1 times more effective in utilizing complex compounds. Accordingly, bacteria strongly outcompete fungi for simple substrates, while fungi take advantage of complex compounds. Bacteria also compete with fungi for the products released during the degradation of complex substrates. Based on these specifics, we differentiated spatial, temporal, and chemical niches for these two groups in soil. The competition will increase under the main five global changes including elevated CO2, N deposition, soil acidification, global warming, and drought. Elevated CO2, N deposition, and warming increase bacterial dominance, whereas soil acidification and drought increase fungal competitiveness.

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细菌-真菌竞争土壤资源的机制和影响

阐明细菌和真菌之间复杂的相互作用，决定土壤中微生物群落的结构、组成和功能，并调节碳 (C) 和养分通量，对于理解生物地球化学循环至关重要。在各种相互作用中，资源竞争是决定土壤中两大微生物类群适应和生态位分化的主要因素。这是因为微生物生长的碳和能量限制是一个规则而不是例外。在这里，我们回顾了细菌和真菌（土壤中的两个主要王国）的碳和能量需求，它们对这些资源和其他资源的竞争机制，导致生态位分化，以及全球变化对这种竞争的影响。标准化的微生物利用偏好表明，细菌在吸收简单有机化合物作为底物方面的效率高出 1.4-5 倍，而真菌在利用复杂化合物方面的效率高出 1.1-4.1 倍。因此，细菌在简单底物方面远远胜过真菌，而真菌则利用复杂化合物。细菌还与真菌竞争复杂底物降解过程中释放的产物。根据这些细节，我们区分了土壤中这两个群体的空间、时间和化学生态位。在二氧化碳排放增加、氮沉降、土壤酸化、全球变暖和干旱等五种主要全球变化的影响下，竞争将加剧。二氧化碳、氮沉降和气候变暖增加了细菌的优势，而土壤酸化和干旱则增加了真菌的竞争力。