Morphological, Histological Changes and Acetyl Cholinesterase Activity in Chick Embryos After Exposure to Abamectin Insecticide

Abamectin is a bio-insecticide, derived from the soil bacteria Streptomyces avermitilis. This insecticide is used in public health and agriculture to protect crops. Major adverse impacts of Abamectin are neurological symptoms acting on the peripheral nervous system. The aim of the current study is to reveal the toxic effects of Abamectin on chick embryo Ross 308 including morphological and histological changes and acetyl cholinesterase activity. 120 fresh fertilized eggs were divided into 6 groups; two of them were used as control. After 2 days of incubation, the eggs were injected with 100 µL of Abamectin solution (diluted at concentrations 360, 540, 900 and 1800 ppm) into the yolk sac. The Results showed that the mortality increased significantly in chicks treated with Abamectin, but had a lower weight in comparison to the control groups. Treated chicks started hatching at day 22 but were physically weak with drooping limbs, paralysis and then died after 24 hours of hatching. Some chicks did not normally hatch and needed assistance. They characterized by limb defects, failure retraction of yolk sac with bleeding. Histological examination of the liver showed hepatic cell degeneration, congestion in the central vein, infiltration of inflammatory cells and hepatocytes necrosis. Furthermore, the Acetyl cholinesterase enzyme analysis showed a significant decrease in the enzyme activity which leads to inhibition the activity of the body systems. It is concluded that low and high concentration of Abamectin has adverse impacts on chick embryo by changing some of morphological, histological characteristics and acetyl cholinesterase activity.

Design of a Microbial Remediation Inoculation Program for Petroleum Hydrocarbon Contaminated Sites Based on Degradation Pathways

This paper analyzed the degradation pathways of petroleum hydrocarbon degradation bacteria, screened the main degradation pathways, and found the petroleum hydrocarbon degradation enzymes corresponding to each step of the degradation pathway. Through the Copeland method, the best inoculation program of petroleum hydrocarbon degradation bacteria in a polluted site was selected as follows: single oxygenation path was dominated by Streptomyces avermitilis, hydroxylation path was dominated by Methylosinus trichosporium OB3b, secondary oxygenation path was dominated by Pseudomonas aeruginosa, secondary hydroxylation path was dominated by Methylococcus capsulatus, double oxygenation path was dominated by Acinetobacter baylyi ADP1, hydrolysis path was dominated by Rhodococcus erythropolis, and CoA path was dominated by Geobacter metallireducens GS-15 to repair petroleum hydrocarbon contaminated sites. The Copeland method score for this solution is 22, which is the highest among the 375 solutions designed in this paper, indicating that it has the best degradation effect. Meanwhile, we verified its effect by the Cdocker method, and the Cdocker energy of this solution is −285.811 kcal/mol, which has the highest absolute value. Among the inoculation programs of the top 13 petroleum hydrocarbon degradation bacteria, the effect of the best inoculation program of petroleum hydrocarbon degradation bacteria was 18% higher than that of the 13th group, verifying that this solution has the best overall degradation effect. The inoculation program of petroleum hydrocarbon degradation bacteria designed in this paper considered the main pathways of petroleum hydrocarbon pollutant degradation, especially highlighting the degradability of petroleum hydrocarbon intermediate degradation products, and enriching the theoretical program of microbial remediation of petroleum hydrocarbon contaminated sites.

Streptomyces xanthii sp. nov. and Streptomyces roseirectus sp. nov. isolated from a Chinese medicinal plant

Two strains of Actinobacteria, designated CRXT-Y-14T and CRXT-G-22T, were isolated from the healthy leaves and seeds, respectively, of a medicinal plant Xanthium sibiricum. Their taxonomic positions were determined using a polyphasic approach. Strain CRXT-Y-14T produced flexuous chains of smooth-surfaced spores. Strain CRXT-G-22T produced straight chains of smooth-surfaced spores. Their morphological features were consistent with the diagnostic characteristics of members of the genus Streptomyces . The results of 16S rRNA gene sequence analyses indicated two strains represented members of the genus Streptomyces . CRXT-Y-14T shared 99.3, 98.9, 98.8 % sequence similarities to Streptomyces atriruber NRRL B-24165T, Streptomyces avermitilis MA-4680T and Streptomyces davaonensis JCM 4913T, respectively. Whilst CRXT-G-22T exhibited highest similarity to Streptomyces acidiscabies ATCC 49003T (98.9 %). The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that the closest phylogenetic neighbours of strains CRXT-Y-14T and CRXT-G-22T were S. atriruber NRRL B-24165T and S. acidiscabies ATCC 49003T, respectively. The phylogenomic analyses further confirmed the relative relationship between strain CRXT-G-22T and S. acidiscabies ATCC 49003T, but indicated that CRXT-Y-14T could represent a novel species of the genus Streptomyce. However, the average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between CRXT-Y-14T and strain CRXT-G-22T, between CRXT-Y-14T and S. atriruber NRRL B-24165T, and between CRXT-G-22T and S. acidiscabies ATCC 49003T were 85.4 and 23.2 %, 85.8 and 23.9 % and 89.1 and 34.1 %, respectively, far below the 95~96 and 70 % cut-off points recommended for delineating species. Furthermore, these two novel isolates were distinctly differentiated from their relatives in the genus Streptomyces with respect to phenotypic and chemotaxonomic characteristics. On the basis of these data, CRXT-Y-14T and CRXT-G-22T clearly represent two novel species within the genus Streptomyces , for which the names Streptomyces xanthii sp. nov. (type strain CRXT-Y-14T = MCCC 1K04966T= JCM 34527T) and Streptomyces roseirectus sp. nov. (type CRXT-G-22T = MCCC 1K04979T= JCM 34565T) are proposed.

Characterization of Class V DyP-Type Peroxidase SaDyP1 from Streptomyces avermitilis and Evaluation of SaDyPs Expression in Mycelium

DyP-type peroxidases are a family of heme peroxidases named for their ability to degrade persistent anthraquinone dyes. DyP-type peroxidases are subclassified into three classes: classes P, I and V. Based on its genome sequence, Streptomyces avermitilis, eubacteria, has two genes presumed to encode class V DyP-type peroxidases and two class I genes. We have previously shown that ectopically expressed SaDyP2, a member of class V, indeed has the characteristics of a DyP-type peroxidase. In this study, we analyzed SaDyP1, a member of the same class V as SaDyP2. SaDyP1 showed high amino acid sequence identity to SaDyP2, retaining a conserved GXXDG motif and catalytic aspartate. SaDyP1 degraded anthraquinone dyes, which are specific substrates of DyP-type peroxidases but not azo dyes. In addition to such substrate specificity, SaDyP1 showed other features of DyP-type peroxidases, such as low optimal pH. Furthermore, immunoblotting using an anti-SaDyP2 polyclonal antibody revealed that SaDyP1 and/or SaDyP2 is expressed in mycelia of wild-type S. avermitilis.

Gene cloning, functional expression and characterization of a novel GH46 chitosanase from Streptomyces avermitilis (SaCsn46A)

A novel glycoside hydrolase (GH) family 46 chitosanase (SaCsn46A) from Streptomyces avermitilis was cloned and functionally expressed in Escherichia coli Rosetta (DE3) strains. SaCsn46A consists of 271 amino acids, which includes a 34-amino acids signal peptide. The protein sequence of SaCsn46A shows maximum identity (83.5%) to chitosanase from Streptomyces sp. SirexAA-E. Then the mature enzyme was purified to homogeneity through Ni-chelating affinity chromatography with a recovery yield of 78% and the molecular mass of purified enzyme was estimated to be 29 kDa by SDS-PAGE. The recombinant enzyme possessed a temperature optimum of 45 oC and a pH optimum of 6.2, and it was stable at pH ranging from 4.0 to 9.0 and below 30 oC. The Km and Vmax values of this enzyme were 1.32 mg∙mL− 1, 526.32 µM∙mg− 1∙min− 1, respectively (chitosan as substrate). The enzyme activity can be enhanced by Mg2+ and especially Mn2+, which could enhance the activity about 3.62-fold at a 3 mM concentration. The enzyme can hydrolyze a variety of polysaccharides which linked by β-1,4-glycosidic bonds such as chitin, xylan and cellulose, but it could not hydrolyze polysaccharides linked by α-1,4-glycosidic bonds. The results of thin layer chromatography and HPLC showed that the enzyme exhibited an endo-type cleavage pattern and could hydrolyze chitosan to glucosamine (GlcN) and (GlcN)2. This study demonstrated that SaCsn46A is a promising enzyme to produce glucosamine and chitooligosaccharides (COS) from chitosan.