Phenotypic characterization of phage vB_vcM_Kuja.

Bacteriophage therapy targeting the increasingly resistant Vibrio cholerae is highly needed. Hence, studying the phenotypic behavior of potential phages under different conditions is a prerequisite to delivering the phage in an active infective form. The objective of this study was to characterize phage VP4 (vB_vcM_Kuja), an environmental vibriophage isolated from River Kuja in Migori County, Kenya in 2015. The phenotypic characteristics of the phage were determined using a one-step growth curve, restriction digestion profile, pH, and temperature stability tests. The results revealed that the phage is stable through a wide range of temperatures (20-50°C) and maintains its plaque-forming ability at pH ranging from 6 to 12. The one-step growth curve showed a latent period falling between 40 and 60 min, while burst size ranged from 23 to 30 plaque-forming units/10 µl at the same host strain. The restriction digestion pattern using EcoRI, SalI, HindIII, and XhoI enzymes showed that HindIII could cut the phage genome. The phage DNA could not be restricted by the other three enzymes. The findings of this study can be used in future studies to determine phage-host interactions.

Novel PhoH-encoding vibriophages with lytic activity against environmental Vibrio strains.

Cholera is a devastating diarrheal disease that accounts for more than 10% of children's lives worldwide, but its treatment is hampered by a rise in antibiotic resistance. One promising alternative to antibiotic therapy is the use of bacteriophages to treat antibiotic-resistant cholera infections, and control Vibrio cholera in clinical cases and in the environment, respectively. Here, we report four novel, closely related environmental myoviruses, VP4, VP6, VP18, and VP24, which we isolated from two environmental toxigenic Vibrio cholerae strains from river Kuja and Usenge beach in Kenya. High-throughput sequencing followed by bioinformatics analysis indicated that the genomes of the four bacteriophages have closely related sequences, with sizes of 148,180 bp, 148,181 bp, 148,179 bp, and 148,179 bp, and a G + C content of 36.4%. The four genomes carry the phoH gene, which is overrepresented in marine cyanophages. The isolated phages displayed a lytic activity against 15 environmental, as well as one clinical, Vibrio cholerae strains. Thus, these novel lytic vibriophages represent potential biocontrol candidates for water decontamination against pathogenic Vibrio cholerae and ought to be considered for future studies of phage therapy.

Antimicrobial activity and phytochemical study of Vernonia glabra (Steetz) Oliv. & Hiern. in Kenya.

Infectious diseases are prevalent and life threatening in Kenya. Majority of the sick are seeking herbal remedies in search of effective, safe, and affordable cure. This project aims to investigate the antimicrobial activity and presence of active phytochemical compounds in different parts of Vernonia glabra; a plant used by herbalists in various regions of Kenya, for the treatment of gastrointestinal problems. The plant sample was collected in January 2010 in Machakos, and different parts dried at room temperature under shade, ground into powder and extracted in Dichloromethane: Methanol in the ratio 1:1, and water. These crude extracts were tested against Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger for antimicrobial activity using disc diffusion technique. Minimum inhibitory concentrations (MICs) for active crude extracts were done using disc diffusion technique after the failure of agar and broth dilution methods. It was observed that the organic crude extracts of flower, leaf, stem, root, and/or entire plant, showed activity against at least one of the four micro-organisms screened, and at concentrations lower than the aqueous crude extracts. Organic crude extract of the leaf showed the highest activity against Staphylococcus aureus (mean inhibition zone of 1.85), recording higher activity than the commercially used standard antibiotic (Streptomycin mean inhibition zone of 1.30). The organic crude extract of flower showed significant activity only against S. aureus, with the lowest MIC of 1.5625 mg/100µl, compared to streptomycin with M.I.C of 6.25 mg/100µl. Thin Layer Chromatography-Bioautography Agar-Overlay showed that, flower alkaloids (50% active), root sapogenins (43.8% active), and root terpenoids (38.5% active) were identified as the potential antibacterial compounds against S. aureus. These results suggest that, V. glabra contains phytochemicals of medicinal properties and justify the use of V. glabra in traditional herbal medicine for the treatment of microbial based diseases. However, research on toxicity which is missing in this study is recommended for V. glabra in order to verify, validate and document the safety of this medicinal plant to the society.

An entomopathogenic Caenorhabditis briggsae.

Caenorhabditis elegans is a premier model organism upon which considerable knowledge of basic cell and developmental biology has been built. Yet, as is true for many traditional model systems, we have limited knowledge of the ecological context in which these systems evolved, severely limiting our understanding of gene function. A better grasp of the ecology of model systems would help us immensely in understanding the functionality of genes and evolution of genomes in an environmental context. Consequently, there are ongoing efforts to uncover natural populations of this model system globally. Here, we describe the discovery of a Caenorhabditis briggsae strain and its bacterial associate (Serratia sp.) that form an entomopathogenic complex in the wild. Laboratory experiments confirm that this nematode and its natural bacterial associate can penetrate, kill and reproduce in an insect host and that the bacterial associate can induce this insect pathogenic life cycle in other Caenorhabditis species, including C. elegans. Our findings suggest that this life history may be widespread in nature and critical to the understanding of the biology of this important model organism. Caenorhabditis-insect interaction could be a key factor in our quest for a better grasp of gene functionality in this important model species. The discovered association, consequently, would provide an ecological framework for functional genomics of Caenorhabditis.