Question

Microbes are extremely difficult to study under the phylogenetic species concept because so much genetic variation results from horizontal rather than vertical gene transfer. Which of the following methods are used to define microbial species?

1) Speciation models that incorporate horizontal gene transfer
2) A threshold of sequence divergence in the 16S rRNA gene
3) The observation that different lineages of microbes adapt to different environmental conditions
4) All of the above are currently used to delineate microbial species

Answer 1

Speciation models, sequence divergence, and adaptation to environmental conditions are methods used to define microbial species. Therefore, the correct answer to how microbial species are defined is: 4) All of the above are currently used to delineate microbial species.

Step-by-step explanation:

The methods used to define microbial species include:

1. Speciation models that incorporate horizontal gene transfer
2. A threshold of sequence divergence in the 16S rRNA gene
3. The observation that different lineages of microbes adapt to different environmental conditions

All of the above methods are currently used to delineate microbial species.

All the methods listed - speciation models incorporating HGT, sequence divergence in the 16S rRNA gene, and observation of adaptation to different environmental conditions - are used to define microbial species in contemporary taxonomy.

Defining microbial species is a complex task due to the prevalence of horizontal gene transfer (HGT), which adds genetic variation in a way that is distinct from the vertical inheritance patterns seen in most multicellular organisms. HGT can make it difficult to represent the evolutionary history of microorganisms with a simple tree of life, leading towards a more interconnected web of life concept. To deal with this complexity, different methods are used to define microbial species:

Creating speciation models that incorporate the effects of horizontal gene transfer.

Establishing a threshold of sequence divergence, particularly within the conserved 16S rRNA gene, which is a standard genetic marker used in prokaryotic taxonomy.

Observing how different lineages of microbes adapt to various environmental conditions, understanding that ecological niches can influence the divergence of species.

Therefore, the correct answer to how microbial species are defined is:

4) All of the above are currently used to delineate microbial species.