Schematic of a mobile genome increasing the diversity of microbial species. Courtesy of the research team
On June 27, Xiaoxue Wang, a researcher at the Key Laboratory of Tropical Marine Biological Resources and Ecology at the South China Sea Institute of Oceanography, Chinese Academy of Sciences, revealed a mechanism for mobile genomes to increase vibrio genome plasticity and drive the genetic and phenotype diversification of Vibrio by studying the interaction between pseudoembranes and Vibrio with ecological competition in corals. The study was published online in The ISME Journal.
Vibrio is one of the most diverse bacterial genera, including the pathogens Vibrio cholerae, Vibrio parahaemolyticis and Vibrio traumatis, which can cause human diseases, as well as Vibrio coral, Vibrio rochae and Vibrio algae that infect fish, corals and other marine invertebrates. Vibrio is an important member of the coral symbiotic population, with diverse metabolic activities, involved in the metabolism of organic matter and elemental circulation of coral symbiotes. Most of the vibrio have the characteristics of fast growth, strong motility, and strong biofilm formation ability, and are prone to overgrowth in complex organic matter-rich areas to reduce the diversity of coral symbiotic microbial species and affect coral health. Comparing the microbial diversity of healthy and diseased coral individuals, it was found that the microbial diversity of corals was significantly reduced after infection with disease.
Pseudoembranus is an important taxon of coral symbiotic microorganisms, which have the same nutrient utilization as Vibrio, occupy the same ecological niche, and will frequently compete with each other. Previous studies have found that Pseudoechomonas is considered a potential coral probiotic because it can directly kill Vibrio by secreting active compounds, or inhibit quorum sensing.
The researchers used a noninvasive sampling method established earlier by the team to isolate the dominant pseudoechomonas and Vibrio algalys from the digestive circulation chambers of healthy clump helmet-shaped corals. The study found that some mutant strains of Vibrio vibrio are produced when Vibrio algae are co-cultured with Pseudoembrania. In-depth mechanistic studies have found that the close collaboration of two autonomously movable genetic elements from the pseudoembranosa genus, an integrative and conjugative element (ICE) and a mobilizable genomic island (MGI), triggers an important “adaptive gene island” (Vibrio phenotype) in Vibrio algae The excision of influencing island, VPII) led to a significant decrease in the biofilm formation capacity and phage resistance of Vibrio algalolyticus, but at the same time its motility was enhanced, which was conducive to expansion into other ecological niches. The study also found that these mobile genome (ICE, MGI, and VPII) members are widely present in Gram-negative bacteria, suggesting that synergies of mobile genetic elements may be very common in increasing the genomic plasticity of microbiome members.
Coral symbiotic bacteria tend to adopt a variety of strategies to inhibit the overgrowth of Vibrio, and the study reports a new strategy in which symbiotic bacteria use mobile genomes to increase the genomic plasticity of competitors, lead to niche differentiation, maintain microbial species diversity in coral symbiotic communities, and provide technical support for the use of coral symbiotic bacteria to maintain the balance of the overall flora of coral symbiotic corals to protect the health of reef-building corals.
Wang Pengxia, associate researcher of the South China Sea Institute of Oceanology of the Chinese Academy of Sciences (a member of the Youth Promotion Association), is the first author of the paper, and Wang Xiaoxue is the corresponding author. The relevant research work has been funded by the Guangdong Provincial Local Innovation Team, the National Natural Science Foundation of China, the Youth Promotion Association of the Chinese Academy of Sciences, and the Guangdong Provincial Laboratory of Southern Marine Science and Engineering (Guangzhou) and other major projects. (Source: China Science Daily, Zhu Hanbin, Ni Songwei)
Related paper information:https://doi.org/10.1038/s41396-022-01272-1