Low abundant soil bacteria can be metabolically versatile and fast growing.

Viola Kurm,Wietse De Boer,W H Gera Hol,Wim H Van Der Putten,Suzanne Naus‐Wiezer

doi:10.1002/ecy.1670

Abstract

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) vs. 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.

Highlights

Many communities contain a few abundant species, whereas most other species are low abundant, or even rare (Magurran and Henderson 2003), so that a general question in ecology is what causes rarity and abundance
There were no significant differences in mean relative abundance of isolates among classes
We did not find relative abundance in soil to be linked to slow growth or restricted substrate use that would have indicated an oligotrophic lifestyle of low abundant species

Summary

Introduction

Many communities contain a few abundant species, whereas most other species are low abundant, or even rare (Magurran and Henderson 2003), so that a general question in ecology is what causes rarity and abundance. As a consequence of this high diversity, the species abundance distribution of microorganisms in soil is even more skewed than of most other species in their habitat, resulting in a long tail of many low abundant species. Some of these species detected by sequencing might be inactive or relic DNA (Carini et al 2016), but many were found to be actively contributing to community dynamics in space and time

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