Termite guts harbor diverse yet-uncultured bacteria, including a non-photosynthetic cyanobacterial group, the class “Melainabacteria”. We herein reported the phylogenetic diversity of “Melainabacteria” in the guts of diverse termites and conducted a single-cell genome analysis of a melainabacterium obtained from the gut of the termite Termes propinquus. We performed amplicon sequencing of 16S rRNA genes from the guts of 60 termite and eight cockroach species, and detected melainabacterial sequences in 48 out of the 68 insect species, albeit with low abundances (0.02–1.90%). Most of the melainabacterial sequences obtained were assigned to the order “Gastranaerophilales” and appeared to form clusters unique to termites and cockroaches. A single-cell genome of a melainabacterium, designated phylotype Tpq-Mel-01, was obtained using a fluorescence-activated cell sorter and whole genome amplification. The genome shared basic features with other melainabacterial genomes previously reconstructed from the metagenomes of human and koala feces. The bacterium had a small genome (~1.6 Mb) and possessed fermentative pathways possibly using sugars and chitobiose as carbon and energy sources, while the pathways for photosynthesis and carbon fixation were not found. The genome contained genes for flagellar components and chemotaxis; therefore, the bacterium is likely motile. A fluorescence in situ hybridization analysis showed that the cells of Tpq-Mel-01 and/or its close relatives are short rods with the dimensions of 1.1±0.2 μm by 0.5±0.1 μm; for these bacteria, we propose the novel species, “Candidatus Gastranaerophilus termiticola”. Our results provide fundamental information on “Melainabacteria” in the termite gut and expand our knowledge on this underrepresented, non-photosynthetic cyanobacterial group.

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Many ant species construct subterranean nests. The presence of their nests may explain soil respiration “hot spots”, an important factor in the high CO2 efflux from tropical forests. However, no studies have directly measured CO2 efflux from ant nests. We established 61 experimental plots containing 13 subterranean ant species to evaluate the CO2 efflux from subterranean ant nests in a tropical seasonal forest, Thailand. We examined differences in nest CO2 efflux among ant species. We determined the effects of environmental factors on nest CO2 efflux and calculated an index of nest structure. The mean CO2 efflux from nests was significantly higher than those from the surrounding soil in the wet and dry seasons. The CO2 efflux was species-specific, showing significant differences among the 13 ant species. The soil moisture content significantly affected nest CO2 efflux, but there was no clear relationship between nest CO2 efflux and nest soil temperature. The diameter of the nest entrance hole affected CO2 efflux. However, there was no significant difference in CO2 efflux rates between single-hole and multiple-hole nests. Our results suggest that in a tropical forest ecosystem the increase in CO2 efflux from subterranean ant nests is caused by species-specific activity of ants, the nest soil environment, and nest structure.

Seven new species occurring on termites are added to Ophiocordyceps – O.asiatica, O.brunneirubra, O.khokpasiensis, O.mosingtoensis, O.pseudocommunis, O.pseudorhizoidea and O.termiticola, based on morphological and molecular phylogenetic evidence. O.brunneirubra possesses orange to reddish-brown immersed perithecia on cylindrical to clavate stromata. O.khokpasiensis, O.mosingtoensis and O.termiticola have pseudo-immersed perithecia while O.asiatica, O.pseudocommunis and O.pseudorhizoidea all possess superficial perithecia, reminiscent of O.communis and O.rhizoidea. Phylogenetic analyses based on a combined dataset comprising the internal transcribed spacer regions (ITS) and the largest subunit (LSU) of the ribosomal DNA, partial regions of the elongation factor 1-α (TEF) and the largest and second largest subunits for the RNA polymerase genes (RPB1, RPB2) strongly support the placement of these seven new species in Ophiocordyceps.

Soil respiration in tropical forests is an important source of carbon dioxide in the atmosphere. Factors regulating spatial soil respiration are still unclear, and they may lead to an inaccurate estimation of soil respiration at the ecosystem level. The aim of this study was to investigate the seasonal changes in spatial variation of soil respiration in a dry evergreen forest of Sakaerat Biosphere Reserve, Nakhon Ratchasima Province, Thailand. Soil respiration, temperature, and moisture were measured in 100 subplots of five 1-ha main plots for four times from November 2014 to August 2016. The average rate ( ± SD) of annual aboveground soil respiration was 6.57 ± 4.29 µmol CO 2 m −2 s −1 . Soil respiration considerably varied with space and time. The mean ranges were from 2.66 to 11.72 µmol CO 2 m −2 s −1 with a maximum rate of 42.68 µmol CO 2 m −2 s −1 . The wet season soil respiration rate (8.81 µmol CO 2 m −2 s −1 ) was two times higher (p < 0.001) than in the dry season (4.33 µmol CO 2 m −2 s −1 ). The seasonal changes clearly affected the spatial variation of soil respiration. Wet season produced higher and more widespread soil respiration. Although soil respiration rates increase with increasing soil temperature and soil moisture content, the rate starts to drop at 27°C soil temperature (p < 0.001) and 21% soil moisture content (p < 0.05). This study suggests more investigation of soil features and animal influences on CO 2 emission hot spots in order to accurately estimate soil respiration in tropical forests.

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Abstract. Jannual N, Nipitwattanaphon M, Hasin S, Kaewgrajang T. 2020. Morphological and molecular characterization of Termitomyces (Lyophyllaceae, Agaricales) in Thailand. Biodiversitas 21: 2481-2491. Termitomyces is considered to be a highly prized delicacy collected both for home consumption and for sale in local markets. Although the taxonomic information about this genus is well known in Africa, the identification of Termitomyces species in Thailand is unclear. Therefore, this study presented an assessment of phylogenetic relationships in the genus Termitomyces by means of sequencing of the ITS1-5.8S-ITS2 region and the species characterization by combination of morphological data and molecular data. Total of 61 Termitomyces specimens was collected from a variety of geographical localities of Thailand. They were classified into six species, including T. clypeatus, T. cylindricus, T. fuliginosus, T. heimii, T. microcarpus, and T. striatus based on morphological characteristics combining with molecular characteristics. This is the first diagnostic key of Thai Termitomyces.

Termites are one of the major contributors to high spatial variability in soil respiration. Although epigeal termite mounds are considered as a point of high CO2 effluxes, the patterns of mound CO2 effluxes are different, especially the mound of fungus-growing termites in a tropical forest. This study quantified the effects of a fungus-growing termite (Macrotermes carbonarius) associated with soil CO2 emission by considering their nesting pattern in dry evergreen forest, Thailand. A total of six mounds of M. carbonarius were measured for CO2 efflux rates on their mounds and surrounding soils in dry and wet seasons. Also, measurement points were investigated for the active underground passages at the top 10% of among efflux rates. The mean rate of CO2 emission from termitaria of M. carbonarius was 7.66 µmol CO2/m2/s, consisting of 2.94 and 9.11 µmol CO2/m2/s from their above mound and underground passages (the rate reached up to 50.00 µmol CO2/m2/s), respectively. While the CO2 emission rate from the surrounding soil alone was 6.86 µmol CO2/m2/s. The results showed that the termitaria of M. carbonarius contributed 8.4% to soil respiration at the termitaria scale. The study suggests that fungus-growing termites cause a local and strong variation in soil respiration through underground passages radiating out from the mounds in dry evergreen forest.