Trends in Ecology & Evolution
ReviewWhy Might Bacterial Pathogens Have Small Genomes?
Section snippets
Reductive Genome Evolution and Pathogenicity (RGEP)
Bacterial pathogens (see Glossary) are one of the most serious threats to human health worldwide, and are evolving resistance to antibiotics at an alarming rate [1]. In a postantibiotic era creative approaches to combating infectious disease will become paramount.
One crucial research goal is to understand why and how bacteria become pathogens. Of course, every instance of pathogen emergence is unique in some way, and they could have little in common. But if we were able to identify any common
Cause, Consequence or Correlate?
One obvious question about RGEP is how or whether the association is causal. At first glance, the comparative evidence argues against a causal relationship. This is because the clearest and best-known examples of bacterial genome reduction include non-pathogens, such as the free-living marine bacteria Pelagibacter and Prochlorococcus 16, 17 and mutualist endosymbionts, such as Buchnera and Portiera 18, 19, 20. Furthermore, the symbionts have a host-restricted and intracellular ecology that is
The Population Genetics of Genome Reduction
A distinct approach to understanding RGEP is to consider the population genetic processes that might lead to bacterial genome reduction (Table 1). This arrangement allows us to draw connections to other examples of reductive genome evolution 3, 20, 37. Here, we ask whether any of the processes has a consistent association with pathogenicity, whether as cause, consequence or correlate.
Concluding Remarks
This article has reviewed the possible association between reductive genome evolution and bacterial pathogenicity (RGEP). One major conclusion is how little we know about this association. Major questions remain about its generality, and how, if at all, the association is causal (see Outstanding Questions).
We have arranged this review according to a third consideration: the population genetic processes that might be involved in genome reduction.
This arrangement cuts across the factors that are
Acknowledgements
We are very grateful to Jane Charlesworth, Eric Miller, Laurence Hurst, and two anonymous reviewers for their helpful suggestions. LW is supported by a Dorothy Hodgkin Fellowship funded by the Royal Society (Grant Number DH140195) and a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (Grant Number 109385/Z/15/Z).
Glossary
- Antivirulence gene
- in the narrow sense, a region of genome that functions to suppress the operation of a virulence gene. More broadly, any region whose removal or inactivation increases virulence.
- Arms race
- evolution of adaptations and counteradaptations during antagonistic coevolution (see also Red Queen).
- Auxotrophic
- unable to synthesise a compound required for growth.
- dN/dS
- in protein-coding sequences, the rate of substitutions that change the amino acid, divided by the rate of synonymous changes
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Ecological life strategies of microbes in response to antibiotics as a driving factor in soils
2023, Science of the Total EnvironmentCitation Excerpt :In contrast, microbes with smaller genomes are specialists, evolving to survive in a specialized habitat (Projan, 2007), which may be seldom helpful in developing antibiotic resistance. For example, multidrug-resistant pathogens with smaller genomes are highly specialized to survive inside animal tissue and perish in other environmental conditions (Weinert and Welch, 2017). Larger genomes also facilitate horizontal gene transfer among distantly related strains, including acquiring antibiotic resistance genes (Barberán et al., 2014).
Metabolic Fate of Human Immunoactive Sterols in Mycobacterium tuberculosis
2021, Journal of Molecular BiologyCitation Excerpt :This point is further supported by a consideration of genome sizes in the Mycobacterium genus (Figure 3). Pathogenic bacteria often have smaller genomes than their non-pathogenic or less-pathogenic relatives – a phenomenon known as reductive genome evolution.26 This is in particular true for the Mycobacterium genus (see Figure 3).
A simple stochastic model describing genomic evolution over time of GC content in microbial symbionts
2020, Journal of Theoretical BiologyCitation Excerpt :Although these pathogens may undergo genome reduction, they do not seem to experience the same dramatic gene loss observed in some symbionts (Moran and Bennett, 2014; Wernegreen, 2015). It is not uncommon, however, for the genomic base composition of intracellular pathogens to be AT-biased but less so than what is observed for microbial symbionts (Weinert and Welch, 2017). There appear to be some similarities between the evolutionary mechanisms of symbionts and those of free-living bacteria that undergo changes in environment even if not through attachment to a host (Batut et al., 2014; Klasson, 2017).
Genome degradation promotes Salmonella pathoadaptation by remodeling fimbriae-mediated proinflammatory response
2023, National Science Review