Characterization of cytoplasmic fibril structures found in gliding cells of Saprospira sp.

Abstract

The cytoplasmic fibril structures of Saprospira sp. strain SS98-5 grown on a low-nutrient agar medium were purified from cell lysates treated with Triton X-100 and were observed by electron microscopy to be about 7 nm in width and 200-300 nm in length. SDS-PAGE of the fibril structures exhibited a single protein band with a molecular mass of 61 kDa. A Saprospira cytoplasmic fibril protein (SCFP), which is a subunit of the fibril structures, was digested with trypsin to oligopeptides and analyzed for amino acid sequences. A partial nucleotide sequence of the SCFP gene was determined after PCR using primers designated from the amino acid sequences of the oligopeptides. SCFP gene including DNA fragments were detected by Southern hybridization using the PCR product for an SCFP gene as a probe and were cloned to determine whole nucleotide sequences. The SCFP gene indicated relatively higher similarity to conserved hypothetical phage tail sheath proteins. A Western immunoblotting analysis showed that SCFP was significantly expressed in gliding cells as compared with nongliding cells. The above findings with the previously reported results suggest that the cytoplasmic fibril structures are possibly related to the gliding motility of Saprospira sp. strain SS98-5.

Comparative Genomics Suggests an Independent Origin of Cytoplasmic Incompatibility in Cardinium hertigii

“…being one of the few characterized components. This protein forms characteristic cytoplasmic fibril structures in Saprospira [53]. Interestingly, transmission electron microscopy shows similar subcellular structures in Cardinium (Figure 3A, 3B) [54]–[56], suggesting the presence of an intact protein secretion system encoded by the AFP-like genes.…”

Interactions between Diatoms and Bacteria

“…5) (60). Further experiments demonstrated that the extracellular structure is a cytoplasmic fibril protein with sequence homology to tail sheath protein domains of bacteriophages (59). Open reading frames (ORFs) adjacent to the gene encoding this fibril protein contain several genes with homology to genes for peptidases and phage-related proteins, indicating a possible role in algicidal activity and a probable phage origin of these genes (191).…”

A Phage Tail-Derived Element with Wide Distribution among Both Prokaryotic Domains: A Comparative Genomic and Phylogenetic Study

“…Afp/PVC were initially grouped with R-type pyocins due to their closer genetic similarity; however, functional studies revealed that they confer toxicity toward insect hemocytes by inducing actin condensation (Yang et al 2006). Two other independent studies demonstrated the presence of fibril-like structures in two unrelated bacterial species: 1) Cardinium hertigii , a member of the Bacteroidetes and symbiont of the parasitic wasp Encarsia pergandiella (Penz et al 2012), and 2) Saprospira SS98-5, a Gram-negative bacterium that exhibits algicidal activity through direct attack and, moreover, is able to prey on Chaetoceros ceratosporum , a eukaryotic bacillariophyte (Furusawa et al 2005). Interestingly, the gene clusters encoding for the fibril-like structures in both species appear to be related to Afp/PVC.…”