Kostas Konstantinidis has challenged the longstanding belief that bacteria do not form distinct species. His new research suggests that bacteria not only form species but also maintain cohesive identities through a process akin to 'sexual' reproduction.
Konstantinidis, the Richard C. Tucker Professor at Georgia Tech's School of Civil and Environmental Engineering, stated, "The next question for us was how individual microbes in the same species maintain their cohesiveness. In other words, how do bacteria stay similar?"
Traditionally, bacteria were thought to evolve primarily through binary fission, a form of asexual reproduction, with infrequent genetic exchange. Using a novel bioinformatic method and extensive genome data, Konstantinidis and his international team tested their hypothesis regarding species emergence and maintenance. Their findings indicate that bacterial evolution and species formation are more 'sexual' than previously understood.
The research was published in the journal Nature Communications. To explore how microbial species retain their identities, the team analyzed complete genomes from two natural populations. They sequenced over 100 strains of Salinibacter ruber from solar salterns in Spain and examined previously published Escherichia coli genomes from livestock farms in the U.K., comparing the genomes of closely related microbes for gene exchange.
The study revealed that 'homologous recombination' plays a crucial role in maintaining microbial species. This process involves microbes exchanging DNA and integrating it into their genomes. The researchers found that recombination occurs frequently and randomly throughout the microbial genome, not limited to specific regions.
Konstantinidis noted, "This may be fundamentally different from sexual reproduction in animals, plants, fungi, and non-bacterial organisms, where DNA is exchanged during meiosis, but the outcome in terms of species cohesion may be similar." The continuous exchange of genetic material fosters cohesion among members of the same species.
The researchers also discovered that individuals within the same species are more likely to exchange DNA with each other than with different species, reinforcing species boundaries.
Konstantinidis remarked, "This work addresses a major, long-lasting problem for microbiology that is relevant for many research areas, namely how to define species and the mechanisms underlying species cohesion."
This research has wide-ranging implications across fields such as environmental science, evolution, medicine, and public health, providing insights for identifying and regulating clinically and environmentally significant organisms. The methodology developed offers a molecular toolkit for future epidemiological and micro-diversity studies.