Exploring the Bioactive Potential of Calostoma insigne, an Endangered Culinary Puffball Mushroom, from Northeastern Thailand.

Calostoma insigne puffball mushrooms are only found in forests with rich biodiversity in very few countries including Thailand, and their biofunctions remain largely unexplored. This study used the agar disk diffusion assay, the anti-glucosidase assay, and the 3, 4, 5-dimethylthiazol-2-yl-2-5-diphenyltetrazolium bromide (MTT) assay to evaluate the bioactive potential of these endangered puffball mushrooms. Internal transcribed spacer (ITS) gene analysis identified C. insigne, a puffball mushroom with green, globose, and spiny spores. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the polysaccharide structure while scanning electron microscopy (SEM) revealed a fiber-like network. The ethanolic gelatinous fruiting body extract exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging capacity (57.96%), a ferric ion-reducing antioxidant power (FRAP) value of 1.73 mg FeSO4/g, and α-glucosidase inhibition (73.18%). C. insigne cytotoxicity was effective towards HT-29 colon cancer cells using the MTT assay (IC50 of 770.6 µg/mL at 72 h) and also showed antiproliferative capacity (IC50 of 297.1 µg/mL). This puffball mushroom stimulated apoptotic genes and proteins (caspase-3, Bax, and p21) via an intrinsic apoptotic pathway in HT-29 cells. In the laboratory, the medium formula consisting of 20% potato, 2% sucrose, and 0.2% peptone was optimal to increase fungal mycelial biomass (2.74 g DW/100 mL), with propagation at pH 5.0 and 30 °C. Puffball mushrooms are consumed as local foods and also confer several potential health benefits, making them worthy of conservation for sustainable utilization.

Formation of Sulforaphane and Iberin Products from Thai Cabbage Fermented by Myrosinase-Positive Bacteria.

Myrosinase-positive bacteria from local fermented foods and beverages in Thailand with the capacity to metabolize glucosinolate and produce isothiocyanates (ITCs) were isolated and used as selected strains for Thai cabbage fermentation. Enterobacter xiangfangensis 4A-2A3.1 (EX) from fermented fish and Enterococcus casseliflavus SB2X2 (EC) from fermented cabbage were the two highest ITC producers among seventeen strains identified by 16S rRNA technique. EC and EX were used to ferment Thai cabbage (Brassica oleracea L. var. capitata) containing glucoiberin, glucoraphanin and 4-hydroxyglucobrassicin at 430.5, 615.1 and 108.5 µmol/100 g DW, respectively for 3 days at 25 °C. Different amounts of iberin nitrile, iberin, sulforaphane and indole 3-acetonitrile were produced by spontaneous, EX- and EC-induced cabbage fermentations, and significantly higher ITCs were detected (p < 0.01) with increased antioxidant activities. Iberin and sulforaphane production in EX-induced treatment peaked on day 2 at 117.4 and 294.1 µmol/100 g DW, respectively, significantly higher than iberin at 51.7 µmol/100 g DW but not significantly higher than sulforaphane at 242.6 µmol/100 g DW in EC-induced treatment at day 2. Maximum health-promoting benefits from this functional food can be obtained from consumption of a liquid portion of the fermented cabbage with higher ITC level along with a solid portion.

Bacterial genospecies that are not ecologically coherent: population genomics of Rhizobium leguminosarum.

Biological species may remain distinct because of genetic isolation or ecological adaptation, but these two aspects do not always coincide. To establish the nature of the species boundary within a local bacterial population, we characterized a sympatric population of the bacterium Rhizobium leguminosarum by genomic sequencing of 72 isolates. Although all strains have 16S rRNA typical of R. leguminosarum, they fall into five genospecies by the criterion of average nucleotide identity (ANI). Many genes, on plasmids as well as the chromosome, support this division: recombination of core genes has been largely within genospecies. Nevertheless, variation in ecological properties, including symbiotic host range and carbon-source utilization, cuts across these genospecies, so that none of these phenotypes is diagnostic of genospecies. This phenotypic variation is conferred by mobile genes. The genospecies meet the Mayr criteria for biological species in respect of their core genes, but do not correspond to coherent ecological groups, so periodic selection may not be effective in purging variation within them. The population structure is incompatible with traditional 'polyphasic taxonomy' that requires bacterial species to have both phylogenetic coherence and distinctive phenotypes. More generally, genomics has revealed that many bacterial species share adaptive modules by horizontal gene transfer, and we envisage a more consistent taxonomic framework that explicitly recognizes this. Significant phenotypes should be recognized as 'biovars' within species that are defined by core gene phylogeny.