10: Biological Environment
- Page ID
- 131887
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“Pure or single population cultures are almost always the creations of microbiologists.”
—Fredrickson and Stephanopoulos (1981)
Microbial communities are multi-species assemblages in which organisms live together and interact (Konopka, 2009). As we have discussed in the previous chapters, abiotic factors such as the chemistry and stability of an environment influence who exists within a community and the reactions that the community carries out (i.e., their function). Coupled with those abiotic controls are biotic interactions such as predation, competition, and mutualism, which can also affect who can grow within a community, as well as their sensitivity to environmental conditions (García et al., 2023). Therefore, we can think of the composition of a microbial community itself as an environmental control on the function and make-up of the community.
In fact, many species cannot grow at all without their partner organisms. As an example, microbiology studies in the past often involved isolation of pure cultures (i.e., those consisting of just one strain of microorganisms). However, with the development of molecular techniques, microbiologists realized that the strains they could grow represented only a tiny fraction of microbial life. Most of microbial life is considered to be uncultivable. One of the factors that can make a species difficult to grow is their dependence on other microbes (Garcia et al., 2015). Cultures are often designed to selectively grow microorganisms with specific capabilities, but such conditions may limit or prevent growth of necessary partner microorganisms.
This chapter describes some of the interactions that occur within microbial communities and then considers a few examples of those interactions. There are many well-documented examples of the interactions between groups of microorganisms and between microorganisms and macroorganisms. An extensive review of such examples is beyond the scope of this book. However, it is useful to examine a few examples to help illustrate the roles of interactions in shaping microbial communities.
- 10.1: Microbial interactions
- Overview of the basic types of microbial interactions, as identified by how each species involved is affected along an axis of positive, negative, or neutral response.
- 10.2: Example interactions
- 10.2.1: Viral predation/parasitism of bacteria
- 10.2.2: Mutualisms between plants and soil microorganisms
- 10.2.3: Interactions of anammox microorganisms with other nitrogen cycles
- 10.2.4: Interactions among iron and sulfur cycling microorganisms
- 10.2.5: Interactions among iron reducers, methanogens, and methanotrophs
- 10.3: Spatial scales of interactions
- Effects of spatial scales on microbial interactions. Indirect interactions through alterations of environmental chemistry.