Isolation and characterization of potential antibiotic producing actinomycetes from water and sediments of Lake Tana,Ethiopia

Objective:To isolate,evaluate and characterize potential antibiotic producing actinomycetes from water and sediments of Lake Tana,Ethiopia.Methods:A total of 31 strains of actinomycetes were isolated and tested against Gram positive and Gram negative bacterial strains by primary screening.In the primary screening.11 promising isolates were identified and subjected to solid state and submerged state fermentation methods to produce crude extracts.The fermented biomass was extracted by organic solvent extraction method and tested against bacterial strains by disc and agar well diffusion methods.The isolates were characterized by using morphological,physiological and biochemical methods.Results:The result obtained from agar well diffusion method was belter than disc diffusion method.The crude extract showed higher inhibition zone against Gram positive bacteria than Cram negative bacteria.One-way analysis of variance confirmed most of the crude extracts were statistically significant at 95%confidence interval.The minimum inhibitor)concentration and minimum bactericidal concentration of crude extracts were 1.65 mg/mL and 3.30 mg/mL against Staphylococcus aureus,and 1.84 mg/mL and 3.80 mg/mL against Escherichia coli respectively.The growth of aerial and substrate mycelium varied in different culture media used.Most of the isolates were able to hydrolysis starch and urea:able to survive at 5%concentration of sodium chloride:optimum temperature for their growth was 30°C.Conclusions:The results of the present study revealed that freshwater actinomycetes of Luke Tana appear to have immense potential as a source ol antibacterial compounds.

Evaluation of water and ethanol extracts of Schinus molle Linn.against immature Culex quinquefasciatus Say(Diptera:Culicidae)

Objective:To evaluate larvicidal and pupicidal activities of aqueous and ethanol extract of different parts of Schinus molle against filarial vector,Culex quinquefasciatus(Cx.quinquefasciatus)in the laboratory.Methods:The mortality rate of third,fourth instar larvae and pupal stages were tested at 20,40,60,80 and 100 mg/L of plant extract using WHO standard protocol with modifications.The mortality rate was recorded continuously for 24,48 and 72 h post exposure period and percentage mortality was calculated.Results:Maximum percentage mortality of third instar was 83.3%in ethanol extract of mature fruit at 100 mg/L after 24 h exposure period.After 48 h exposure period,93.3%percentage mortality was recorded in ethanol extract of immature fruit at 100 mg/L.After 72 h exposure period,100%mortality was recorded in water extract of leaf at 100 mg/L.In fourth instar larvae,maximum percentage mortality of 63.3%was recorded in water extract of mature fruit and ethanol extract of immature and mature fruit at 100 mg/L after 24 h exposure period.After 48 h exposure period 86.6%mortality was recorded in ethanol extract of mature fruit at 100 mg/L.After 72 h exposure period,93.3%mortality was recorded in ethanol extract of mature fruit at 100 mg/L.In general immature Cx.quinquefasciatus,percentage mortality was increased with increase in exposure time and concentration of the plant extracts tested.Conclusions:From this laboratory study,Schinus molle plant parts were proved to have larvicidal and pupicidal activity against immature Cx.quinquefasciatus.