Control of aflatoxigenic strains by Cinnamomum porrectum essential oil.

Essential oil from the bark of Cinnamomum porrectum (Roxb.) Kosterm was obtained by hydrodistillation using a Clevenger-type system for 3 h and identified by gas chromatography-mass spectrometry. The compounds were safrole (93.9%), elemicine (4.3%) and methyl eugenol (1.7%). The effect of essential oil on mycelial growth, sporulation, and aflatoxin B1 production of Aspergillus parasiticus IMI 283883 and Aspergillus flavus IMI 242684 was evaluated using contact and vapor treatments. Aflatoxin B1 was determined using the Enzyme-linked immunosorbent assay. The results showed that C. porrectum (Roxb.) Kosterm essential oil at concentrations more than 200 ppm exhibited inhibition effect on mycelial growth, sporulation, and aflatoxin B1 production of both Aspergillus strains as compared with control. The fumigation activities via vapor treatment showed higher inhibition than contact treatment. This study suggests that C. porrectum (Roxb.) Kosterm essential oil represents a good alternative in eco-friendly control of aflatoxigenic strain on food and agricultural commodities.

Micromonospora soli sp. nov., isolated from rice rhizosphere soil.

An actinomycete strain SL3-70(T) was isolated from a rice field and characterised using a polyphasic approach. The morphological and chemotaxonomical characteristics of strain SL3-70(T) indicate that it belongs to the genus Micromonospora. The phylogenetic analysis of the nearly complete 16S rRNA gene sequence revealed that strain SL3-70(T) is a member of the genus Micromonospora, and is closely related to Micromonospora echinaurantica DSM 43904(T) (99.1 % 16S rRNA gene sequence similarity) and Micromonospora kangleipakensis MBRL 34(T) (98.8 %). DNA-DNA relatedness between strain SL3-70(T) and its relatives ranged from 21.2 % ± 0.6 to 38.7 % ± 0.4. The results obtained from our study indicate that strain SL3-70(T) represents a novel species of the genus Micromonospora, for which the name Micromonospora soli sp. nov. is proposed. The type strain is SL3-70(T) (=BCC 67268(T); =NBRC 110009(T)).

Antimicrobial compounds from endophytic Streptomyces sp. BCC72023 isolated from rice (Oryza sativa L.).

An endophytic actinomycete strain BCC72023 was isolated from rice (Oryza sativa L.) and identified as the genus Streptomyces, based on phenotypic, chemotaxonomic and 16S rRNA gene sequence analyses. The strain showed 99.80% similarity compared with Streptomyces samsunensis M1463(T). Chemical investigation led to the isolation of three macrolides, efomycins M (1), G (2) and oxohygrolidin (3), along with two polyethers, abierixin (4) and 29-O-methylabierixin (5). To our knowledge, this is the first report of efomycin M being isolated from a natural source. The compounds were identified using spectroscopic techniques and comparison with previously published data. All compounds exhibited antimalarial activity against the Plasmodium falciparum, K-1 strain, a multidrug-resistant strain, with IC50 values in a range of 1.40-5.23 µg/ml. In addition, these compounds were evaluated for biological activity against Mycobacterium tuberculosis, Bacillus cereus, Colletotrichum gloeosporioides and Colletotrichum capsici, as well as cytotoxicity against both cancerous (MCF-7, KB, NCI-H187) and non-cancerous (Vero) cells.

Micromonospora oryzae sp. nov., isolated from roots of upland rice.

An actinomycete strain, designated CP2R9-1T, was isolated from root internal tissues of upland rice (Oryza sativa). Based on a polyphasic approach, strain CP2R9-1T was characterized as a member of the genus Micromonospora. meso-Diaminopimelic acid and 3-OH-diaminopimelic acid were present in the cell-wall peptidoglycan. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, two unidentified phospholipids and four unidentified polar lipids. Predominant menaquinones were MK-9(H4), MK-9(H6) and MK-10(H4). Whole-cell sugars consisted of ribose, xylose, arabinose and glucose. Phylogenetic analysis of the nearly complete 16S rRNA gene sequence suggested that strain CP2R9-1T was closely related to Micromonospora haikouensis 232617T (99.32 % similarity), Micromonospora carbonacea DSM 43168T (99.18 %) and Micromonospora krabiensis MA-2T (99.16 %). Strain CP2R9-1T was distinct from its closest relatives based on low levels of DNA-DNA relatedness (21.3 ± 0.1-41.7 ± 0.7 %) and phenotypic differences. The results presented in this study showed that strain CP2R9-1T represents a novel species of the genus Micromonospora, for which the name Micromonospora oryzae sp. nov. is proposed. The type strain is CP2R9-1T ( = BCC 67266T = NBRC 110007T).

Micromonospora endophytica sp. nov., an endophytic actinobacteria of Thai upland rice (Oryza sativa).

An actinobacterial strain, DCWR9-8-2(T), was isolated from a leaf of Thai upland rice (Oryza sativa) collected in Chumporn province, Thailand. Strain DCWR9-8-2(T) is Gram-stain-positive aerobic bacteria that produce single spores directly on the vegetative hypha. Cell wall peptidoglycan of this strain exhibits meso-diaminopimelic acid and glycine, the reducing sugars of whole-cell hydrolysate are arabinose, glucose, ribose, xylose and small amount of mannose. The phospholipid profiles in the membrane are comprised of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides. The major menaquinones are MK-9(H4) and MK-10(H6). The diagnostic cellular fatty acids are iso-C16:0 and iso-C15:0. The G+C content of the genomic DNA is 72.5 mol%. The result of 16S rRNA sequence analysis of the strain revealed that this strain was closely related to Micromonospora auratinigra TT1-11(T) (99.25%). On the other hand, the result of gyrB gene sequence analysis revealed that this strain was closed to M. eburnea JCM 12345(T) (96.30%). In addition, a combination of DNA-DNA hybridization results and some phenotypic properties supported that this strain should be judged as a novel species of the genus Micromonospora, for which the name M. endophytica sp. nov. is proposed. The type strain is DCWR9-8-2(T) (=BCC 67267(T)=NBRC 110008(T)).