Autolysis of Chlorella variabilis in Starving Paramecium bursaria Help the Host Cell Survive Against Starvation Stress.

The endosymbiosis between Paramecium bursaria and Chlorella spp. is mutualistic. Symbiotic algae localize beneath the host Paramecium cell cortex compete for their attachment sites with preexisting organelle trichocysts. To examine the relationship between P. bursaria trichocysts and their symbiotic algae, algae-bearing or alga-free P. bursaria were starved for several days and the changes in the number of Chlorella sp. and presence or absence of trichocysts were evaluated. We conducted an indirect immunofluorescence microscopy with an anti-trichocyst monoclonal antibody against P. bursaria cells. Indirect immunofluorescence microscopy demonstrated that under starvation and darkness conditions, the immunofluorescence of trichocysts in alga-free P. bursaria decreased much faster than that in the normal algae-bearing P. bursaria. In the latter case, our observations proposed the possibility that the nutrition obtained from symbiotic algal digestion may promote trichocysts synthesis. This algal digestion mechanism may permit host P. bursaria cells to survive for a longer time under starvation condition. To the best of our knowledge, this may be a new benefit that host P. bursaria gain from harboring symbiotic algae.

Virgisporangium myanmarense sp. nov., a novel motile actinomycete isolated from an anthill soil in Myanmar.

An actinomycete strain, designated MM04-1133T, was isolated from an anthill soil sample collected in Bagan, Myanmar. To establish the taxonomic status of this strain, the isolate was subjected to a polyphasic approach. Strain MM04-1133T was Gram-staining positive, aerobic, motile and formed long and narrow sporangia directly above the surface of the substrate mycelium. Whole-cell hydrolysates of the strain contained 3-OH-diaminopimelic acid, arabinose, glucose, galactose, mannose, rhamnose and xylose. The predominant menaquinones were MK-10(H6) and MK-10(H8). The major cellular fatty acids were iso-C16:0 and anteiso-C17:0. The diagnostic phospholipid was phosphatidylethanolamine. The G+C content of the DNA was 69.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequence revealed that strain MM04-1133T clustered within the genus Virgisporangium, with the sequence exhibiting highest similarity (98.5% identity) with Virgisporangium ochraceum NBRC 16418T. The strain grew in the presence of 0-1% (w/v) NaCl, at pH 5-8 and at 20-40 °C, with optimal growth at 30-37 °C. Based on phylogenetic analysis and chemotaxonomic and phenotypic data, we propose classifying this isolate as a novel species of the genus Virgisporangium, to be designated as Virgisporangium myanmarense sp. nov. The type strain is MM04-1133T (=NBRC 112733T=VTCC 910008T).