A cellulose-degrading defined mixed culture (designated SF356) consisting of five bacterial strains (Clostridium straminisolvens CSK1, Clostridium sp. strain FG4, Pseudoxanthomonas sp. strain M1-3, Brevibacillus sp. strain M1-5, and Bordetella sp. strain M1-6) exhibited both functional and structural stability; namely, no change in cellulose-degrading efficiency was observed, and all members stably coexisted through 20 subcultures. In order to investigate the mechanisms responsible for the observed stability, "knockout communities" in which one of the members was eliminated from SF356 were constructed. The dynamics of the community structure and the cellulose degradation profiles of these mixed cultures were determined in order to evaluate the roles played by each eliminated member in situ and its impact on the other members of the community. Integration of each result gave the following estimates of the bacterial relationships. Synergistic relationships between an anaerobic cellulolytic bacterium (C. straminisolvens CSK1) and two strains of aerobic bacteria (Pseudoxanthomonas sp. strain M1-3 and Brevibacillus sp. strain M1-5) were observed; the aerobes introduced anaerobic conditions, and C. straminisolvens CSK1 supplied metabolites (acetate and glucose). In addition, there were negative relationships, such as the inhibition of cellulose degradation by producing excess amounts of acetic acid by Clostridium sp. strain FG4, and growth suppression of Bordetella sp. strain M1-6 by Brevibacillus sp. strain M1-5. The balance of the various types of relationships (both positive and negative) is thus considered to be essential for the stable coexistence of the members of this mixed culture.

A stable cellulose-degrading microflora enriched from composting materials has been analyzed in our laboratory. Cellulose-degrading efficiency of an anaerobic cellulolytic isolate, Clostridium straminisolvens CSK1, was remarkably lower than that of the original microflora. We successfully constructed bacterial communities with effective cellulose degradation by mixing C. straminisolvens CSK1 with aerobic non-cellulolytic bacteria isolated from the original microflora. Comparison of the cellulose degradation processes of the pure culture of C. straminisolvens CSK1 and the mixed-culture indicated that non-cellulolytic bacteria essentially contribute to cellulose degradation by supplying anaerobic environment, consuming metabolites, which otherwise deteriorate the cellulolytic activity, and by neutralizing pH.

We investigated the network relationships of bacteria in a structurally stable mixed culture degrading cellulose. The mixed culture consists of four bacterial strains (a cellulose-degrading anaerobe [strain S], a saccharide-utilizing anaerobe [strain F], a peptide- and acetate-utilizing aerobe [strain 3] and a peptide-, glucose-, and ethanol-utilizing aerobe [strain 5]). Interspecies interactions were examined by analyzing the effects of culture filtrates on the growth of the other strains and by comprehensively analyzing population dynamics in the mixed-culture systems with all possible combinations of the four bacterial strains. The persistence of strain S depends on the effects of strain 5. However, strain 5 is a disadvantaged strain because strain 3 has bacteriocidal activity on strain 5. The extinction of strain 5 is indirectly prevented by strain F that suppresses the growth of strain 3. Although strain F directly has suppressive effects on the growth of strain S, strain F is essential for the persistence of strain S, considering the indirect effects (maintaining strain 5, which is essential for the survival of strain S, by inhibiting strain 3). These indirect relationships form a bacterial network in which all the relationships including suppressive effects were well balanced to maintain the structural stability. In addition to direct metabolite interactions, such kind of indirect relationships could have a great impact on microbial community structure in the natural environment.

Photodynamic agents, due to their photon‐dependent selective activation, can selectively activate a number of physiological processes and may directly modulate signal transduction in a number of cells including pancreatic acinar cells. Activation of the photodynamic agent sulphonated aluminium phthalocyanine (SALPC) triggered recurrent cytosolic calcium ([Ca2+]i) spiking in pancreatic acinar cells. The photodynamically triggered calcium spiking could be blocked by phosphatidylinositol‐specific phospholipase C (PI‐PLC) inhibitor U73122, but not by phosphatidylcholine‐specific phospholipase C inhibitor D609. Removal of extracellular Ca2+ abolished spiking, as did 2‐aminoethoxydiphenylborate (2‐APB), an inhibitory modulator of IP3‐mediated Ca2+ release from intracellular stores. These data suggest that SALPC photodynamic action may permanently fix PI‐PLC in an active conformation, and this produced recurrent [Ca2+]i spiking.

A novel anaerobic, thermophilic and cellulolytic bacterium (strain CSK1 T ) was isolated from a cellulose-degrading bacterial community. On the basis of 16S rRNA gene sequence similarity, strain CSK1 T was mapped to cluster III of the genus Clostridium. Strain CSK1 T is closely related to Clostridium thermocellum (96?2 %) and Clostridium aldrichii (95?1 %). Strain CSK1 T is a non-motile, spore-forming, straight or slightly curved rod. The optimum temperature and initial pH for its growth and cellulose degradation are 50-55 6C and pH 7?5. Strain CSK1 T grew under a gas phase containing up to 4 % O 2 . Phylogenetic and phenotypic analyses support the differentiation of strain CSK1 T from its closest relatives. Strain CSK1 T therefore represents a novel species, for which the name Clostridium straminisolvens sp. nov. is proposed, with CSK1 T (=DSM 16021 T =IAM 15070 T ) as the type strain.