Genomic analysis of Isoptericola halotolerans SM2308 reveals its potential involved in fucoidan degradation

Marine bacteria play important roles in the degradation and recycling of algal polysaccharides. However, the marine bacteria involved in fucoidan degradation and their degradation pathways remain poorly understood. Here, we report the complete genome sequence of Isoptericola halotolerans SM2308, isolated from a brown algal sample collected from an intertidal zone of the Yellow Sea in China. The genome of strain SM2308 consists of a single circular chromosome of 4,011,455 bp with a high GC content of 72.70 %. Strain SM2308 exhibited rapid growth on fucoidan as the sole carbon source, indicating its capacity to degrade fucoidan. Gene annotation and metabolic pathway analyses showed that strain SM2308 possesses a complete pathway for utilizing fucoidan, including the extracellular breakdown of polymeric fucoidan into smaller fucooligosaccharides/fucose by fucoidanases, the transmembrane transport of fucooligosaccharides/fucose into the cytoplasm by an ABC transporter, and the intracellular fucose catabolism via a non-phosphorylative pathway. This represents the first genome of an actinobacterium from the order Micrococcales with fucoidan-degrading ability. The genome of Isoptericola halotolerans SM2308 provides insights into the role of actinobacteria in the biogeochemical cycling of fucoidan in marine ecosystems.