Accepted_test

Bacteria exhibit a continuum from free-living to symbiotic lifestyles, which is accompanied by modifications in their genomes [1]. Symbiotic bacteria can have beneficial effects on the host organism, acting as mutualists. Alternatively, they may have negative effects, in which case, the bacterium is termed a pathogen. Additionally, intermediate forms known as opportunistic bacteria can switch their behavior depending on environmental conditions. These lifestyles can coexist within a single bacterial genus.
Among the structures that mediate the establishment of symbiosis, the O-antigen, the distal component of the bacterial cell envelope lipopolysaccharide [2], plays a pivotal role. It captures molecular signals from the host and facilitates the entry of the bacterium into the organism. The O-antigen is the first responder to changes in environmental conditions: entry into a new niche, bacteriophage attack, and abiotic factors. For this reason, the structure of the somatic antigen is highly variable [3].
The establishment of symbiosis involves reduction of the bacterial genome, leading to the loss of a number of coding elements. Typically, these are genes that become redundant due to a change in niche. We hypothesize that the O-antigen, which mediates the connection with the host organism, is subject to modification in bacteria with different lifestyles (mutualists, opportunists, and pathogens). For comparative analysis, bacteria from the genus Herbaspirillum, characterized by different lifestyles, were selected.