Intracolony variation of bacterial gut microbiota among castes and ages in the fungus-growing termite Macrotermes gilvus.

The fungus-growing termites Macrotermes cultivate the obligate ectosymbiontic fungi, Termitomyces. While their relationship has been extesively studied, little is known about the gut bacterial symbionts, which also presumably play a crucial role for the nutrition of the termite host. In this study, we investigated the bacterial gut microbiota in two colonies of Macrotermes gilvus, and compared the diversity and community structure of bacteria among nine termite morphotypes, differing in caste and/or age, using terminal restriction fragment length polymorphism (T-RFLP) and clonal analysis of 16S rRNA. The obtained molecular community profiles clustered by termite morphotype rather than by colony, and the clustering pattern was clearly more related to a difference in age than to caste. Thus, we suggest that the bacterial gut microbiota change in relation to the food of the termite, which comprises fallen leaves and the fungus nodules of Termitomyces in young workers, and leaves degraded by the fungi, in old workers. Despite these intracolony variations in bacterial gut microbiota, their T-RFLP profiles formed a distinct cluster against those of the fungus garden, adjacent soil and guts of sympatric wood-feeding termites, implying a consistency and uniqueness of gut microbiota in M. gilvus. Since many bacterial phylotypes from M. gilvus formed monophyletic clusters with those from distantly related termite species, we suggest that gut bacteria have co-evolved with the termite host and form a microbiota specific to a termite taxonomic and/or feeding group, and furthermore, to caste and age within a termite species.

Isolation and identification of the cyanotoxin cylindrospermopsin and deoxy-cylindrospermopsin from a Thailand strain of Cylindrospermopsis raciborskii (Cyanobacteria).

A strain of Cylindrospermopsis (Cyanobacteria) isolated from a fishpond in Thailand was examined for its taxonomy based upon morphology and 16S rRNA gene sequence. It was also examined for production of the hepatotoxic cyanotoxin called cylindrospermopsin (CYN) and deoxycylindrospermopsin (deoxy-CYN). The strain (CY-Thai) was identified as C. raciborskii (Woloszynska) Seenaya and Subba Raju based upon morphological examination which was confirmed by 16S rRNA gene sequences and phylogenetic comparisons based upon its 16S rRNA gene. The alkaloid heptatotoxin CYN was confirmed using mouse bioassay, HPLC and HPLC-MS/MS while deoxy-CYN was confirmed using HPLC-MS/MS. The mouse bioassay gave a minimum lethal dose at 250mg dry weight cells/kg body weight within 24h and 125mg/kg at 72h, with signs of poisoning the same as in literature reports for CYN. HPLC chromatographic comparison of the CY-Thai toxin with standard CYN gave the same retention time and an absorbance maximum at 262nm. HPLC-MS/MS confirmed the presence of CYN (M+H 416) and deoxy-CYN (M+H 400). The CYN content in strain CY-Thai was estimated at 1.02mg/g and approximately 1/10 of this amount for deoxy-CYN. This is the first report from Asia of a CYN, deoxy-CYN producing Cylindrospermopsis raciborskii.

Utilization of volatile fatty acids from the anaerobic digestion liquor of sewage sludge for 5-aminolevulinic acid production by photosynthetic bacteria.

Using volatile fatty acids (VFA) from the anaerobic digestion liquor of sewage sludge, up to 9.2 mM 5-aminolevulinic acid (ALA) could be produced by Rhodobacter sphaeroides under anaerobic-light (5 kLux) conditions with repeated addition of levulinic acid (LA) and glycine and using a large inoculum (approx. 2 g/l of cells, initially from glutamate/malate medium). As the VFA medium also contained organic nitrogen sources such as glutamic acid, the cells were later grown up to about 2 g/l in the VFA medium instead of the glutamate/malate medium. ALA production was then again promoted by adding LA and glycine. Using this improved method, up to 9.3 mM ALA was produced by feeding propionate and acetate together with LA and glycine, indicating that VFA medium formed from sewage sludge could be useful for ALA production.