Data from: Low abundant soil bacteria can be metabolically versatile and fast growing

The abundance of species is assumed to depend on their life history traits, such as growth rate and resource specialization. However, this assumption has not been tested for bacteria. Here we investigate how abundance of soil bacteria relates to slow growth and substrate specialization (oligotrophy) versus fast growth and substrate generalization (copiotrophy). We collected 47 saprotrophic soil bacterial isolates of differing abundances and measured their growth rate and the ability to use a variety of single carbon sources. Opposite to our expectation, there was no relationship between abundance in soil and the measured growth rate or substrate utilization profile (SUP). However, isolates with lower growth rates used fewer substrates than faster growing ones supporting the assumption that growth rate may relate to substrate specialization. Interestingly, growth rate and SUP were correlated with phylogeny, rather than with abundance in soil. Most markedly, Gammaproteobacteria on average grew significantly faster and were able to use more substrates than other bacterial classes, whereas Alphaproteobacteria were growing relatively slowly and used fewer substrates. This finding suggests that growth and substrate utilization are phylogenetically deeply conserved. We conclude that growth rate and substrate utilization of soil bacteria are not general determinants of their abundance. Future studies on explaining bacterial abundance need to determine how other factors, such as competition, predation and abiotic factors may contribute to rarity or abundance in soil bacteria.物种丰度通常被认为与其生活史性状（life history traits）密切相关，例如生长速率与资源特化能力。然而，这一假设尚未在细菌类群中得到验证。本研究旨在探究土壤细菌的丰度与慢速生长、底物特化（贫营养（oligotrophy））以及快速生长、底物泛化（富营养（copiotrophy））之间的关联。我们收集了47株不同丰度的腐生土壤细菌分离株，并测定了其生长速率以及利用多种单一碳源的能力。与我们的预期相悖，土壤细菌的丰度与测得的生长速率或底物利用谱（substrate utilization profile, SUP）并无关联。不过，生长速率较低的分离株相较于生长较快的菌株，可利用的底物更少，这支持了"生长速率可能与底物特化相关"的假设。有趣的是，生长速率与底物利用谱均与系统发育背景相关，而非与土壤中的细菌丰度相关。最为显著的是，γ-变形菌纲（Gammaproteobacteria）平均生长速率显著快于其他细菌纲，且可利用的底物更多；而α-变形菌纲（Alphaproteobacteria）生长相对缓慢，可利用的底物更少。这一发现表明，生长与底物利用特性在系统发育上具有高度保守性。我们由此得出结论：土壤细菌的生长速率与底物利用能力并非决定其丰度的通用因子。未来旨在阐释细菌丰度的研究，需要明确竞争、捕食以及非生物因子等其他因素如何影响土壤细菌的稀有性与丰度。