Neomycin biosynthesis is regulated positively by AfsA-g and NeoR in Streptomyces fradiae CGMCC 4.7387.

Neomycins are a group of aminoglycoside antibiotics with both clinical and agricultural applications. To elucidate the regulatory mechanism of neomycin biosynthesis, we completed draft genome sequencing of a neomycin producer Streptomyces fradiae CGMCC 4.7387 from marine sediments, and the neomycin biosynthesis gene cluster was identified. Inactivation of the afsA-g gene encoding a γ-butyrolactone (GBL) synthase in S. fradiae CGMCC 4.7387 resulted in a significant decrease of neomycin production. Quantitative RT-PCR analysis revealed that the transcriptional level of neoR and the aphA-neoGH operon were reduced in the afsA-g::aac(3)IV mutant. Interestingly, a conserved binding site of AdpA, a key activator in the GBL regulatory cascade, was discovered upstream of neoR, a putative regulatory gene encoding a protein with an ATPase domain and a tetratricopeptide repeat domain. When neoR was inactivated, the neomycin production was reduced about 40% in comparison with the WT strain. Quantitative RT-PCR analysis revealed that the transcriptional levels of genes in the aphA-neoGH operon were reduced clearly in the neoR::aac(3)IV mutant. Finally, the titers of neomycin were improved considerably by overexpression of afsA-g and neoR in S. fradiae CGMCC 4.7387.

Significance of hind wing morphology in distinguishing genera and species of cantharid beetles with a geometric morphometric analysis.

There remain some difficulties in delimitation of related genera or sibling species for cantharid beetles, because the traditionally taxonomic method and morphological characters have not been updated or introduced. In the present study, we firstly use the landmark-based geometric morphometrics to analyze and compare the hind wings of nine species belonging to three genera of Cantharinae to ascertain whether this approach may be used as a reliable method in the study of the taxonomy of this group. The results show that the shape differences of the hind wings among genera seem more variable than that within each genus, and the variations for each species are different from one another, as shown in the principal component analyses. And the canonical variates analyses show that there are significant differences among the genera and the species of each genus, which demonstrates that the hind wing shape can be diagnostic for both generic and specific identification of the cantharid beetles. This study sheds new light into clarifying the taxonomic uncertainties of Cantharidae, and lays a foundation for further studies on the evolution of the cantharid hind wing shape.

Taxonomy of Fissocantharis Pic (Coleoptera, Cantharidae) from Guangxi, China, with descriptions of six new species.

A total of 17 species of Fissocantharis Pic is recorded from Guangxi, China. Six species are described new to science, Fissocantharissinensomima sp. n., Fissocantharissexcostata sp. n., Fissocantharisbasilaris sp. n., Fissocanthariseschara sp. n., Fissocantharislatipalpa sp. n. and Fissocantharisbiprojicientis sp. n., and two previously known species are redescribed, Fissocantharisgracilipes (Pic, 1927) and Fissocantharissinensis (Wittmer, 1988). These species are presented with habitus of males, abdominal sternites VIII of females and genitalia of both sexes. Fissocantharisflavofacialis (Pic, 1926) is synonymized with Fissocantharisangusta (Fairmaire, 1900); both were originally described in the genus Podabrus Westwood. Additionally, a key and a checklist of all the species of Fissocantharis from Guangxi are provided.