The present study aimed to isolate and characterize a marine bacterium capable of passing through a 0.1-μm pore-sized filter (0.1-μm filter). Sediment suspension samples were filtered through 0.1-μm filters, inoculated into sterile media, and incubated. Isolated SspURN76 belonged to Saccharospirillum, according to 16S rRNA gene sequencing, and showed a very slender shape. The minimum cell size of SspURN76 was 0.09×3.2‍ ‍μm. These morphological features of SspURN76 were likely responsible for its passage through 0.1-μm filters. Based on the results obtained herein, marine bacteria may be present in 0.1-μm filtered fractions.