Abstract:

Due to the complexity and variability of marine environments, marine bacteria may have evolved unique environmental adaptation mechanisms. Genomic islands usually carry genes related to the environmental adaptation of host bacteria and play an important role in driving bacterial adaptation and genome diversification. Pseudoalteromonas is an important genus that is widely distributed in various marine habitats, and has attracted attention due to the important industrial application and ecological restoration potential. In this study, we focused on Pseudoalteromonas sp. SM9913 isolated from marine sediments. By comparative genomics analysis of SM9913 with the closely related strain Pseudoalteromonas haloplanktis TAC125 isolated from surface seawater, an 18-kb genomic island GIPspSM9913 integrated in the yicC gene was identified. This genomic island encodes an integrase and an excisionase, as well as multiple restriction modification systems. Sequence analysis showed that GIPspSM9913 homologs are widely distributed in marine bacteria such as Pseudoalteromonas, Shewanella, Vibrio and Aeromonas. Quantitative PCR assays showed that GIPspSM9913 can excise when the excisionase is produced, resulting in the removal of GIPspSM9913. Sequencing analysis indicated that excision of GIPspSM9913 did not affect the expression of flanking genes. We also compared the swimming motility, electroporation efficiency and conjugation efficiency of the GIPspSM9913 deleted strain and the wild-type strain SM9913, and found that the presence of GIPspSM9913 can increase the swimming motility of the host bacteria and offer the host defense against the invasion of foreign DNA.

Key words: marine bacteria, Pseudoalteromonas, genomic island, motility, environmental adaptation