Versatile Chemo-Biocatalytic Cascade Driven by a Thermophilic and Irreversible C-C Bond-Forming α-Oxoamine Synthase.

We report a chemo-biocatalytic cascade for the synthesis of substituted pyrroles, driven by the action of an irreversible, thermostable, pyridoxal 5'-phosphate (PLP)-dependent, C-C bond-forming biocatalyst (ThAOS). The ThAOS catalyzes the Claisen-like condensation between various amino acids and acyl-CoA substrates to generate a range of α-aminoketones. These products are reacted with ß-keto esters in an irreversible Knorr pyrrole reaction. The determination of the 1.6 Å resolution crystal structure of the PLP-bound form of ThAOS lays the foundation for future engineering and directed evolution. This report establishes the AOS family as useful and versatile C-C bond-forming biocatalysts.

Miswak (Salvadora persica) modulated the growth performance, antioxidative response, and histopathological damage induced by zinc toxicity in Nile tilapia (Oreochromis niloticus).

In this study, Nile tilapia fingerlings with average body weight (8.6 ± 0.06 g) were exposed to zinc (Zn) toxicity and tested its amelioration with miswak (Salvadora persica L.) (SP) supplemented diet. Five fish groups were fed on diets with SP at 0, 0.25, 0.5, 1.0, and 2.0% (T1, T2, T3, T4, and T5, respectively) diet without Zn exposure, while another five groups were exposed to Zn at 7 mg/L and co-supplemented with SP at 0, 0.25, 0.5, 1.0, and 2.0 % (T6, T7, T8, T9, and T10, respectively). After 12 weeks, fish-fed 1.0% SP diet (T4) achieved the highest growth and feed performances, while the lowest one was in Zn-exposed fish (T6) (P < 0.05). T6 and T7 groups showed the most inferior carcass protein and ash contents, while T4 and T5 showed the highest lipid content (P < 0.05). The level of Zn residue increased in fish exposed to Zn (P < 0.05). Fish exposed to Zn and fed SP showed high blood urea, catalase, ALT, AST, and total superoxide dismutase (T-SOD), while the malondialdehyde (MDA) was decreased (P < 0.05). Interestingly, miswak resulted in elevated catalase and T-SOD and reduced MDA in fish without Zn exposure (P < 0.05). Zn exposure causes abnormal histopathological characteristics in gills, hepatopancreas, posterior kidney, and musculature tissues of tilapia, while fish-fed SP showed regular, healthy, and protected histopathological characters. The results suggested that SP can induce the antioxidant responses that prepare Nile tilapia for a further suppressive oxidative condition (i.e., Zn exposure).

Ziziphus mauritiana supplementation of Nile tilapia (Oreochromis niloticus) diet for improvement of immune response to Aeromonas hydrophila infection.

This study evaluated the effectiveness of dietary Ziziphus mauritiana leaf powder (ZLP) to control Aeromonas hydrophila infection in Nile tilapia and reduce damage to vital immune organs. Four experimental groups were fed a diet supplemented with ZLP at concentrations of 0, 5, 10, and 20 g/kg (w/w) for 6 weeks. At the end of the feeding trial, all groups were intraperitoneally injected with pathogenic A. hydrophila. It was found that Z. mauritiana significantly (P < 0.05) upregulated (lysozyme, interleukin 1 beta) and superoxide dismutase gene expressions as well as improved the activity of serum lysozyme and liver antioxidant enzymes. The fish that were fed a ZLP-supplemented diet also exhibited significantly higher survival rates after A. hydrophila challenge than those that were fed a ZLP-free diet (P < 0.05). Supplementation of 10 g/kg ZLP most effectively reduced the histopathological alterations caused by A. hydrophila challenge in the liver, spleen, kidney, and muscle of the fish. In conclusion, ZLP can be effective in controlling A. hydrophila infection in Nile tilapia (particularly at a concentration of 10 g/kg) through enhancement of its immune and antioxidant status.

Molecular identification of Trichodina compacta Van As and Basson, 1989 (Ciliophora: Peritrichia) from cultured Oreochromis niloticus in Egypt and its impact on immune responses and tissue pathology.

Trichodinids are peritrichous ciliated protozoa that affect both wild and cultured fishes. Several Trichodina species have low host specificity and are morphologically distinct, facilitating their identification based primarily on the presence of adhesive discs and the number of attached denticles. A trichodinid species named Trichodina compacta was first reported by Van As and Basson (1989) (Protozoa: Ciliophora: Peritrichia). However, in trichodinid infestations, morphological characteristics are insufficient for identifying the infesting species. Therefore, molecular and phylogenetic analyses are considered to be promising and useful tools for identifying the infesting species. This study aimed to achieve the molecular identification of a trichodinid infestation in Nile tilapia and to construct the phylogenetic relationships between the identified species and other peritrichous parasites. Moreover, we also aimed to study the pathological and immunological impacts of trichodinids on fry tissue to improve our understanding of the immune responses of teleost fish to trichodinae parasitic infestations and develop a better control method. Here, we used molecular techniques to identify the isolated trichodina species as T. compacta and demonstrated that Trichodina infestation in Nile tilapia is associated with remarkable immunogenic and inflammatory responses (increased il-1ß expression and decreased il-8 and tgf-ß expression). These findings improve our understanding of the responses of teleost fish to trichodinid parasite infestation and will be helpful for the development of novel control strategies that reverse the inflammatory and immunogenic alterations that occur in infested fish.

Molecular characterization, antibiotic resistance pattern and biofilm formation of Vibrio parahaemolyticus and V. cholerae isolated from crustaceans and humans.

Human infection with pathogenic vibrios is associated with contaminated seafood consumption. In the present study, we examined 225 crustaceans collected from retail markets in Egypt. Stool samples from gastroenteritis patients were also examined. Bacteriological and molecular examinations revealed 34 (15.1%) V. parahaemolyticus and 2 (0.9%) V. cholerae from crustaceans, while V. parahaemolyticus isolates were identified in 3 (3%) of the human samples. The virulence-associated genes tdh and/or trh were detected in 5.9% and 100% of the crustacean and human samples, respectively, whereas the two V. cholerae isolates were positive for the ctx and hlyA genes. Antibiotic sensitivity revealed high resistance of the isolates to the used antibiotics and an average MAR index of 0.77. Biofilm formation at different temperatures indicated significantly higher biofilm formation at 37 °C and 25 °C compared with 4 °C. Frequent monitoring of seafood for Vibrio species and their antibiotic, molecular and biofilm characteristics is essential to improve seafood safety.

Dietary fucoidan enhance the non-specific immune response and disease resistance in African catfish, Clarias gariepinus, immunosuppressed by cadmium chloride.

Fucoidan is sulfated polysaccharide extracted from seaweed brown algae. This study was designed to evaluate the immunomodulatory effects and disease resistance of dietary fucoidan on catfish, Clarias gariepinus, immunosuppressed by cadmium. Three hundred and sixty African catfish, C. gariepinus, was allocated into six equal groups. The first group served as a control. Groups (F1 and F2) were fed on fucoidan supplemented ration at concentrations of 4 and 6g/kg diet respectively for 21 days. Groups (Cd, CdF1 and CdF2) were subjected throughout the experiment to a sub-lethal concentration of 5ppm cadmium chloride solution and groups (CdF1 and CdF2) were fed on a ration supplemented with fucoidan. Macrophages oxidative burst, phagocytic activity percentages and lymphocytes transformation index were a significant increase in the fucoidan-treated groups (F1 and F2), while serum lysozyme, nitric oxide and bactericidal activity were enhanced only in group (F2) when compared with controls. These parameters as well as absolute lymphocyte count and survival rate were significantly increased in group (CdF2) when compared with cadmium chloride immunosuppressed group (Cd). It could be concluded that the fucoidan can be used as immunostimulant for the farmed African catfish, C. gariepinus as it can improve its resistance to immunosuppressive stressful conditions.

Seafood a potential source of some zoonotic bacteria in Zagazig, Egypt, with the molecular detection of Listeria monocytogenes virulence genes.

This article describes the results of a study conducted on 71 fresh seafood samples (fish and shellfish) marketed in Zagazig city, Sharkia province, Egypt, as well as on 50 human stool samples collected at the Zagazig University Hospital. The samples were examined for the presence of Listeria monocytogenes and Escherichia coli. The investigation of L. monocytogenes virulence genes was performed using Polymerase Chain Reaction (PCR), while the microbiological quality of the seafood samples was evaluated using the coliform count and aerobic plate count (APC) as indicators. Out of the examined 71 seafood samples, 20 (28.2%) were identified as L. monocytogenes, 15 (75%) of which were confirmed as virulent strains. Also, out of 50 human stool samples, only 1 (2%) was identified as virulent L. monocytogenes. E. coli serotypes were isolated from only 11.3% of seafood and 30% of human stool samples. In shellfish, the APC and most probable number of coliforms (MPC) were higher than those obtained from other fish samples. Multiplex PCR targeting internalin genes allowed simultaneous identification of L. monocytogenes and differentiation of virulent strains, thus enabling more timely detection of cases and sources of food borne listeriosis. The article concludes by stressing that the isolation of potentially virulent L. monocytogenes and E. coli from both seafood samples and humans emphasises the potential public health hazard caused by eating raw or undercooked shellfish.

Immunomodulatory effect of dietary Saccharomyces cerevisiae, beta-glucan and laminaran in mercuric chloride treated Nile tilapia (Oreochromis niloticus) and experimentally infected with Aeromonas hydrophila.

Six hundred and forty Nile tilapia (Oreochromis niloticus) weighing 80-100g were randomly allocated into eight equal groups (80 each). The first group acts as control. Groups S, B and L were fed on a ration supplemented with Saccharomyces cerevisiae, beta-glucans and laminaran, respectively for 21 days. Groups M, MS, MB and ML were subjected throughout the experiment to sublethal concentration of mercuric chloride (0.05 ppm). Gps. MS, MB and ML were fed on a ration containing S. cerevisiae, beta-glucan and laminaran respectively for 21 days. Fish were challenged with Aeromonas hydrophila (0.4 x 10(7) cells mL(-1)) via intra-peritoneal injection and the mortality rate was recorded up to 10 day post-challenge. The non-specific defense mechanisms, cellular and humoral immunity, beside the total and differential leukocytic count were determined. Lymphocyte transformation index, phagocytic activity percent, phagocytic index, total lymphocyte count, serum bactericidal activity and nitric oxide as well as the survival rate were insignificantly changed after 21 day in gps. MS&ML, when compared with mercuric chloride immune depressed group M. These parameters as well as the neutrophil adhesion, serum nitric oxide and survival rate were significantly increased in gp. MB when compared with gp. M. Meanwhile the cellular and humoral immunity beside the survival rate were significantly increased in groups S, B, L when compared with control group. It could be concluded that the whole yeast S. cerevisiae, beta-glucan and laminaran can be used as immunostimulants for the farmed Nile tilapia. The beta-glucans could be used in farmed Nile tilapia, under immune depressive stressful condition to increase their resistance to diseases.