Genetic diversity and differentiation analysis reveals geographical structure characteristics of Dermatophagoides farinae (Acari: Pyroglyphidae).

Dermatophagoides farinae (Acari: Pyroglyphidae) has been reported as one of the major sources of indoor allergens that trigger allergic disease in humans. In this study, the genetic diversity and differentiation of nine geographic populations of D. farinae were investigated by analyzing mitochondrial and nuclear genes (COI, Cytb, COI+Cytb, and ITS). The results showed high genetic diversity across the D. farinae populations. The BX (Benxi) population showed the lowest genetic diversity, possibly due to climatic causes. Significant genetic differentiation was observed among D. farinae populations based on mitochondrial genes. The analysis of molecular variance (AMOVA) results elucidated that the contribution to the rate of variation was primarily from among populations. Phylogenetic analysis and haplotype network based on mitochondrial genes both indicated significant geographic structure among D. farinae populations. The nine geographic populations of D. farinae were divided into two groups with the Qinling Mountains-Huai River Line serving as the boundary for spatial analysis of molecular variance analysis (SAMOVA). However, the Mantel test analysis showed no association between genetic differentiation and geographic distance because of the high level of gene flow among some populations through the transportation of stored food. Overall, these results indicate both significant genetic differentiation among D. farinae populations, but also significant gene exchange between them. Results from the analysis of the nuclear gene ITS differed from the mitochondrial genes due to differences in molecular markers between mitochondrial genes and nuclear genes. These observations improve our understanding of the genetic diversity and structure of D. farinae populations.

Identification of a Novel Class of Photolyases as Possible Ancestors of Their Family.

UV irradiation induces the formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts in DNA. These two types of lesions can be directly photorepaired by CPD photolyases and 6-4 photolyases, respectively. Recently, a new class of 6-4 photolyases named iron-sulfur bacterial cryptochromes and photolyases (FeS-BCPs) were found, which were considered as the ancestors of all photolyases and their homologs-cryptochromes. However, a controversy exists regarding 6-4 photoproducts only constituting ∼10-30% of the total UV-induced lesions that primordial organisms would hardly survive without a CPD repair enzyme. By extensive phylogenetic analyses, we identified a novel class of proteins, all from eubacteria. They have relatively high similarity to class I/III CPD photolyases, especially in the putative substrate-binding and FAD-binding regions. However, these proteins are shorter, and they lack the "N-terminal α/ß domain" of normal photolyases. Therefore, we named them short photolyase-like. Nevertheless, similar to FeS-BCPs, some of short photolyase-likes also contain four conserved cysteines, which may also coordinate an iron-sulfur cluster as FeS-BCPs. A member from Rhodococcus fascians was cloned and expressed. It was demonstrated that the protein contains a FAD cofactor and an iron-sulfur cluster, and has CPD repair activity. It was speculated that this novel class of photolyases may be the real ancestors of the cryptochrome/photolyase family.

A rapid identification method for common astigmatid species based on multiplex polymerase chain reaction.

Astigmatid mites are economically significant pests of stored products and sources of inhalant allergens causing allergic rhinitis and asthma worldwide. The morphological identification of astigmatid mites at the species level is often a difficult task due to their small size, phenotypic similarity and lack of diagnostic characters. We used multiplex polymerase chain reaction (PCR) to identify astigmatid mite species, which could complement the morphological data for the species-specific identification of mites. Internal ribosomal transcribed spacer (ITS) sequences (i.e., partial 18S, the full length of ITS1-5.8S-ITS2 and partial 28S) from eight astigmatid species (Acarus siro, Tyrophagus putrescentiae, Suidasia nesbitti, Dermatophagoides pteronyssinus, Dermatophagoides farinae, Lepidoglyphus destructor, Chortoglyphus arcuatus and Gohieria fuscus) were obtained by DNA extraction and then sequenced after PCR amplification. Specific primers were designed in the ITS2 region manually. Results revealed that an identification method for eight common astigmatid species was established based on multiplex PCR, which should be effective for the identification of other species of mites by redesigning species-specific primers in future experiments.

Cloning and knockout of phytoene desaturase gene in Sphingomonas elodea ATCC 31461 for economic recovery of gellan gum.

A gene encoding phytoene desaturase (crtI) in the carotenoid biosynthetic pathway of Sphingomonas elodea ATCC 31461, an industrial gellan gum-producing strain, was cloned and identified. This gene is predicted to encode a 492-amino acid protein with significant homology to the phytoene desaturase of other carotenogenic organisms. Knockout of crtI gene blocked yellow carotenoid pigment synthesis and resulted in the accumulation of colorless phytoene, confirming that it encodes phytoene desaturase. Further research indicates that the yield of gellan gum production by crtI gene knockout mutants is almost the same as that by the wild-type strain. In addition, a recovery method based on the colorless fermentation broth of the crtI gene knockout mutant was investigated. Compared to the volume of alcohol for the parent strain, much less alcohol (30%) is required in this recovery process; thus, the costs of downstream purification of gellan gum can be substantially reduced.

Drug resistance marker-aided genome shuffling to improve acetic acid tolerance in Saccharomyces cerevisiae.

Acetic acid existing in a culture medium is one of the most limiting constraints in yeast growth and viability during ethanol fermentation. To improve acetic acid tolerance in Saccharomyces cerevisiae strains, a drug resistance marker-aided genome shuffling approach with higher screen efficiency of shuffled mutants was developed in this work. Through two rounds of genome shuffling of ultraviolet mutants derived from the original strain 308, we obtained a shuffled strain YZ2, which shows significantly faster growth and higher cell viability under acetic acid stress. Ethanol production of YZ2 (within 60 h) was 21.6% higher than that of 308 when 0.5% (v/v) acetic acid was added to fermentation medium. Membrane integrity, higher in vivo activity of the H+-ATPase, and lower oxidative damage after acetic acid treatment are the possible reasons for the acetic acid-tolerance phenotype of YZ2. These results indicated that this novel genome shuffling approach is powerful to rapidly improve the complex traits of industrial yeast strains.

Molecular evidence of coinfection of Anaplasma species in small ruminants from Anhui Province, China.

The species of the genus Anaplasma are obligate intracellular pathogens that threaten the health of both humans and animals. In this study, we investigated the presence of Anaplasma phagocytophilum, A. ovis and A. bovis in 203 healthy small ruminants (117 goats and 86 sheep) in Anhui Province, China. The overall coinfection of Anaplasma species occurred in 33.0% (67/203) of all studied samples. The infection rates of A. ovis, A. bovis, and A. phagocytophilum were 14.5%, 12.0%, and 4.3% in goats and 26.7%, 17.4% and 3.5% in sheep, respectively. Coinfection of A. ovis + A. bovis was predominant in this study, with overall rates of 21.4% in goats and 20.9% in sheep, while the overall coinfection rates of A. ovis + A. phagocytophilum and A. bovis + A. phagocytophilum were 7.7% and 2.6% in goats and 7.0% and 4.7% in sheep, respectively. The occurrence of three-pathogen coinfection was also found in the studied ruminants, with a rate of 0.9% in goats and 1.2% among sheep. Phylogenetic analysis based on msp4 sequences showed that there were differences in the A. ovis genotype between sheep and goats in this study.

A novel strategy to construct yeast Saccharomyces cerevisiae strains for very high gravity fermentation.

Very high gravity (VHG) fermentation is aimed to considerably increase both the fermentation rate and the ethanol concentration, thereby reducing capital costs and the risk of bacterial contamination. This process results in critical issues, such as adverse stress factors (ie., osmotic pressure and ethanol inhibition) and high concentrations of metabolic byproducts which are difficult to overcome by a single breeding method. In the present paper, a novel strategy that combines metabolic engineering and genome shuffling to circumvent these limitations and improve the bioethanol production performance of Saccharomyces cerevisiae strains under VHG conditions was developed. First, in strain Z5, which performed better than other widely used industrial strains, the gene GPD2 encoding glycerol 3-phosphate dehydrogenase was deleted, resulting in a mutant (Z5ΔGPD2) with a lower glycerol yield and poor ethanol productivity. Second, strain Z5ΔGPD2 was subjected to three rounds of genome shuffling to improve its VHG fermentation performance, and the best performing strain SZ3-1 was obtained. Results showed that strain SZ3-1 not only produced less glycerol, but also increased the ethanol yield by up to 8% compared with the parent strain Z5. Further analysis suggested that the improved ethanol yield in strain SZ3-1 was mainly contributed by the enhanced ethanol tolerance of the strain. The differences in ethanol tolerance between strains Z5 and SZ3-1 were closely associated with the cell membrane fatty acid compositions and intracellular trehalose concentrations. Finally, genome rearrangements in the optimized strain were confirmed by karyotype analysis. Hence, a combination of genome shuffling and metabolic engineering is an efficient approach for the rapid improvement of yeast strains for desirable industrial phenotypes.

The combination of glycerol metabolic engineering and drug resistance marker-aided genome shuffling to improve very-high-gravity fermentation performances of industrial Saccharomyces cerevisiae.

A challenge associated with the ethanol productivity under very-high-gravity (VHG) conditions, optimizing multi-traits (i.e. byproduct formation and stress tolerance) of industrial yeast strains, is overcome by a combination of metabolic engineering and genome shuffling. First, industrial strain Y12 was deleted with a glycerol exporter Fps1p and hetero-expressed with glyceraldehydes-3-phosphate dehydrogenase, resulting in the modified strain YFG12 with lower glycerol yield. Second, YFG12 was subjected to three rounds of drug resistance marker-aided genome shuffling to increase its ethanol tolerance, and the best shuffled strain TS5 was obtained. Compared with wild strain Y12, shuffled strain TS5 not only decreased glycerol formation by 14.8%, but also increased fermentation rate and ethanol yield by 3.7% and 7.6%, respectively. Moreover, the system of genetic modification and Cre/loxP in aid of three different drug-resistance markers presented in the study significantly improved breeding efficiency and will facilitate the application of breeding technologies in prototrophic industrial microorganisms.

Screening and construction of Saccharomyces cerevisiae strains with improved multi-tolerance and bioethanol fermentation performance.

In this study, a systemic analysis was initially performed to investigate the relationship between fermentation-related stress tolerances and ethanol yield. Based on the results obtained, two elite Saccharomyces cerevisiae strains, Z8 and Z15, with variant phenotypes were chosen to construct strains with improved multi-stress tolerance by genome shuffling in combination with optimized initial selection. After three rounds of genome shuffling, a shuffled strain, YZ1, which surpasses its parent strains in osmotic, heat, and acid tolerances, was obtained. Ethanol yields of YZ1 were 3.11%, 10.31%, and 10.55% higher than those of its parent strains under regular, increased heat, and high gravity fermentation conditions, respectively. YZ1 was applied to bioethanol production at an industrial scale. Results demonstrated that the variant phenotypes from available yeast strains could be used as parent stock for yeast breeding and that the genome shuffling approach is sufficiently powerful in combining suitable phenotypes in a single strain.

Optimization of process variables for the manganese peroxidase of the white-rot fungus Schizophyllum sp. F17 by full factorial central composite design.

White-rot fungus manganese peroxidase (MnP) that has great potential in degrading azo dyes is one of the extracellular glycolsylated heme proteins. MnP from Schizophyllum sp. F17 was isolated and purified by Sephadex G-75 gel filtration chromatography followed by DEAE-cellulose anion exchange chromatography. The molecular weight of the puried enzyme was 49.2 kDa, while the half-life of the MnP in the presence of 0.1 mmol/L H2O2 was 5-6 min. The efficiency of MnP-catalyzed reactions were determined by three key factors: the concentrations of Mn2+, H2O2, and the amount of MnP. Using single factor analysis, an optimized concentration of Mn2+, H2O2 and enzyme were optimized to be 1.2 mmol/L, 0.1 mmol/L, and 0.4 mL, respectively. A response surface methodology (RSM) employing two-level-three-factor full factorial central composite design was used to optimize the catalytic conditions. The result showed that the concentration of H2O2 and the interaction between H2O2 and MnP mostly affect the MnP catalytic efficiency. Finally, we show that the azo dyes could be efficiently decolorized by the purified MnP under optimized conditions.