A polyphasic study of Aspergillus section Flavi isolated from corn in Guangxi, China- a hot spot of aflatoxin contamination.

Aspergillus section Flavi is widely known as a potential threat to contaminate agricultural products and food commodities. In this study, a polyphasic approach consisting of micro- and macro-morphological, chemical and molecular features, was applied to survey the Aspergillus section Flavi population in corn collected from Guangxi, China. Based on multigene phylogenies as well as morphological observations, Aspergillus flavus (192/195), A. arachidicola (1/195), A. pseudonomius (1/195) and A. novoparasiticus (1/195) were found to be the predominant section Flavi population. Among them, 31 representative isolates were selected for mycotoxin determination. The results showed that Aspergillus flavus chemotype I was most common, chemotype IV was also detected with low incidence and low CPA amounts, while chemotypes II and III were absent. Other tested species including A. arachidicola, A. pseudonomius, and A. novoparasiticus produced all types of aflatoxins, but none of them produced CPA. The polyphasic approach applied in this study permitted reliable understanding of the prevailing Aspergillus section Flavi population and their mycotoxin profiles. Knowledge of the prevailing section Flavi population will aid in developing a sustainable strategy to mitigate the effects of aflatoxin contamination. This study suggests that CPA contamination of food should be considered while conducting mycotoxigenic surveys of food commodities, and the same should be considered while planning a bio-control strategy to control aflatoxin contamination.

Thermostaphylospora grisealba gen. nov., sp. nov., isolated from mushroom compost and transfer of Thermomonospora chromogena Zhang et al. 1998 to Thermostaphylospora chromogena comb. nov.

A novel thermophilic actinomycete, designated strain 3-12XT, was isolated from mushroom compost in Guangxi University, Nanning, China. The novel isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and the whole-cell sugars were glucose and ribose. The predominant menaquinones were MK-9(H4) and MK-9(H6). The polar phospholipids were diphosphatidylglycerol, hydroxy-phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, ninhydrin-positive phosphoglycolipids and glycolipids. Major fatty acids were so-C16 : 0 and C17 : 0. The G+C content of the genomic DNA was 74.6 %. The 16S rRNA gene sequence analysis showed that the closest phylogenetic neighbour of strain 3-12XT was Thermomonospora chromogena ATCC 43196T (97.0 %), other closely related strains all belonged to the family Streptosporangiaceae and showed more than 6 % divergence. The chemotaxonomic characteristics of strain 3-12XT were significantly different from Thermomonospora chromogena ATCC 43196T and DNA-DNA hybridization showed low relatedness (48.6-55.6 %) between them, so they should be different species. Thermomonospora chromogena was removed from the genus Thermomonospora by Zhang et al. 1998 on the basis of phylogenetic, chemotaxonomic and phenotypic evidence, but its taxonomic position remains uncertain. Based on the phenotypic and phylogenetic data, strain 3-12XT represents a novel species in a new genus in the family Streptosporangiaceae. The name Thermostaphylospora griseoalba gen. nov., sp. nov. is proposed. The type strain of Thermostaphylospora grisealba is 3-12XT (=DSM 46781T=CGMCC 4.7160T). We also propose transferring Thermomonospora chromogenaZhang et al. 1998 to Thermostaphylospora chromogena comb. nov. (type strain ATCC 43196T=JCM 6244T).

Streptomyces thermoalkaliphilus sp. nov., an alkaline cellulase producing thermophilic actinomycete isolated from tropical rainforest soil.

During an investigation exploring potential sources of novel thermophilic species and natural products, a novel thermophilic and alkaliphilic actinomycete with alkaline cellulase producing ability, designated strain 4-2-13T, was isolated from soil of a tropical rainforest in Xishuangbanna, Yunnan province, China. The morphological and chemotaxonomic characteristics of strain 4-2-13T are consistent with those of the members of the genus Streptomyces. The strain forms extensively branched aerial mycelia and substrate mycelia. Spiral spore chains were observed on aerial mycelia; spores were oval to cylindrical, with smooth surfaces. The organism was found to contain LL-diaminopimelic acid as the diagnostic diamino acid in the cell wall peptidoglycan. The whole cell hydrolysates were found to contain glucose and ribose. The cellular fatty acid profile mainly consists of anteiso-C17:0 and iso-C16:0. The menaquinones were identified as MK-9(H8), MK-10(H6) and MK-9(H6). The polar lipids profile were found to consist of diphosphatidylglycerol, phosphatidylmethylethanolamine, a ninhydrin-positive glycophospholipid, phosphatidylinositol, phosphatidylglycerol and unidentified glycolipids. The 16S rRNA gene sequence analysis showed that the organism belongs to the genus Streptomyces and in the 16S rRNA gene tree it formed a distinct phyletic line together with the closely related type strain Streptomyces burgazadensis Z1R7T (95.2% sequence similarity). However, the phenotypic characteristics of strain 4-2-13T are significantly different from those of S. burgazadensis Z1R7T. Based on the phenotypic, chemotaxonomic and phylogenetic characteristics, strain 4-2-13T represents a novel species in the genus Streptomyces, for which the name Streptomyces thermoalkaliphilus sp. nov. is proposed. The type strain is 4-2-13T (= DSM 42159T = CGMCC 4. 7205T).