Genomics of Clostridium taeniosporum, an organism which forms endospores with ribbon-like appendages

Clostridium taeniosporum, a non-pathogenic anaerobe closely related to the C. botulinum Group II members, was isolated from Crimean lake silt about 60 years ago. Its endospores are surrounded by an encasement layer which forms a trunk at one spore pole to which about 12–14 large, ribbon-like appendages are attached. The genome consists of one 3,264,813 bp, circular chromosome (with 26.6% GC) and three plasmids. The chromosome contains 2,892 potential protein coding sequences: 2,124 have specific functions, 147 have general functions, 228 are conserved but without known function and 393 are hypothetical based on the fact that no statistically significant orthologs were found. The chromosome also contains 101 genes for stable RNAs, including 7 rRNA clusters. Over 84% of the protein coding sequences and 96% of the stable RNA coding regions are oriented in the same direction as replication. The three known appendage genes are located within a single cluster with five other genes, the protein products of which are closely related, in terms of sequence, to the known appendage proteins. The relatedness of the deduced protein products suggests that all or some of the closely related genes might code for minor appendage proteins or assembly factors. The appendage genes might be unique among the known clostridia; no statistically significant orthologs were found within other clostridial genomes for which sequence data are available. The C. taeniosporum chromosome contains two functional prophages, one Siphoviridae and one Myoviridae, and one defective prophage. Three plasmids of 5.9, 69.7 and 163.1 Kbp are present. These data are expected to contribute to future studies of developmental, structural and evolutionary biology and to potential industrial applications of this organism.

Clostridium taeniosporum is a close relative of the Clostridium botulinum Group II

Clostridium taeniosporum is a Gram-positive, anaerobic, rod-shaped non-toxigenic organism isolated from Crimean lake silt. It is unique in forming spores from which about twelve large, flat, ribbon-like appendages emanate. These ribbon-like structures, about 4.5 microm long and 0.45 microm wide, are assembled from smaller fibrils with 5 nm diameter spherical heads attached to thin tails about 1-2 nm in diameter and about 40 nm in length. The appendages have four major components, a glycoprotein with a collagen-like region, two proteins each of which contains two conserved domains of unknown function, and an ortholog of the Bacillus subtilis spore morphogenetic protein SpoVM. Genes for three of these and other, possibly related proteins, cluster on two chromosome fragments. Here we report that C. taeniosporum is saccharolytic, non-proteolytic, and produces both acetic and butyric acid fermentation products. It synthesizes alpha-D-glucosidase and N-acetyl-beta,D-glucoseaminidase constitutively. These physiological properties are similar to those of the C. botulinum Group II. Genotypically, C. taeniosporum is also closely related to the same Group II, based on 16S rDNA sequences. C. taeniosporum differs from typical C. botulinum Group II strains because it is non-toxigenic and in forming the ribbon-like spore appendages. These major differences among otherwise closely related organisms suggest lateral transfer of genes for appendage synthesis and for toxigenicity.

Clostridium taeniosporum spore ribbon-like appendage structure, composition and genes

Clostridium taeniosporum spores have about 12 large, flat, ribbon-like appendages attached through a common trunk at one spore pole to a previously unknown surface layer outside the coat that is proposed to be called the 'encasement'. Appendages are about 4.5 microm long, 0.5 microm wide and 30 nm thick and taper at the attachment end into a semicircle that is twisted relative to the flat ribbon. Individual fibrils, about 45 nm in length with spherical heads and long thin tails, form a hair-like nap, visible along the appendage edge. Four appendage proteins have been detected: a paralogous pair of 29 kDa (designated P29a and P29b), a glycoprotein of about 37 kDa (designated GP85) and an orthologue of the Bacillus spore morphogenetic protein SpoVM. The P29 proteins consist of duplicated regions and each region includes a domain of unknown function 11. The GP85 glycoprotein contains a collagen-like region. The genes for P29a and b, GP85 and possibly related proteins are closely linked on two small chromosome fragments. Putative sigma(K)-dependent promoters upstream of the P29a and b genes indicate that they likely are expressed late in the mother cell, consistent with their deposition into the layer external to the coat.