What Bacteria Are Present in the Endosphere of Lettuce Seeds and Why?

Increasing demand for high-quality food is driving the development of biologized farming methods, which involve the use of microorganisms, including endophytes, to stimulate plant growth. However, research on the composition of endosphere microbiomes is limited. The study presents an analysis of the bacterial endophytic microbiome in lettuce seeds (Lactuca sativa L., cv. Ozornik) using high-throughput sequencing of 16S rRNA amplicons. It evaluates the taxonomic composition and putative functional properties of seed endophytic bacteria. The microbial community exhibited low diversity (Shannon index ranged from 1.1 to 1.84, Simpson index from 0.57 to 0.83). The bacterial endophytic community of lettuce seeds was dominated by Pseudomonadota (83%), Actinomycetota (14%), and Bacillota (3%). The genera identified within the microbiome included Pantoea (32%), Rhodococcus (13%), Candidatus Profftella (13%), Janthinobacterium (7%), Pseudomonas (9%), Enterococcus (3%), and Alcaligenes (2%), which exhibit a broad spectrum of beneficial properties: plant growth promotion (PGPB), suppression of phytopathogens, enhanced stress tolerance, participation in contaminant biodegradation, and heavy metal detoxification. The structure and functional potential of the microbiome vary between samples, potentially due to differences in source material and cultivation conditions. The obtained results expand our understanding of the composition and functions of endophytic bacteria in lettuce seeds, which is important for the development of novel biocontrol agents for plants consumed by humans in an unprocessed form.