Studies on bacterioplankton and inhibitory strains of aquatic actinomycetes in Lake Bardawil, Egypt

Abstract

Lake Bardawil represents a hyper-saline shallow (50-600 cm deep) water basin lying along the northern shore of Sinai. Surface water samples were collected monthly from this lake for physico-chemical and microbiological analysis. Seasonal variations in the averages of temperature, pH and transparency of the tested water samples were determined. Seasonal averages of the total bacterial counts at 22 and 37°C, biovolumes of cells and bacterial biomass of the lake's water at different regions were also determined. In addition to the gram-negative pathogen, Edwardsiella tarda, faecal contamination indicators, total coliforms, faecal coliforms and faecal streptococci were counted in the lake's water samples from various regions during different seasons. The number of actinomycetes per milliliter of the lake's water samples were determined. Fifteen actinomycetes were isolated and screened for their antibacterial activity against E. coli and pathogenic E. tarda isolated from the same water samples. Five isolates of these actinomycetes showed antibacterial activities and nine of them were identified as Streptomyces. The most antibacterially active isolate was subjected to morphological, physiological and biochemical studies and identified as Streptomyces viridiviolaceus. The identified organism exhibited antimicrobial activities against the main indicator of water pollution, E. coli, pathogenic E. tarda, Corynebacterium michiganese B-33, Pseudomonas solanacearum B-3212 and Staphylococcus. No antimicrobial activities were recorded against Bacillus cereus, Micrococcus, Mycobacterium, Aspergillus niger, Candida albicans, C. tropicalis or Rhizopus nigricans.

Microbial contamination of vegetable crop and soil profile in arid regions under controlled application of domestic wastewater

“…Samples were immediately transferred in ice tank to the Lab. Physical and chemical characteristics were determined as described before (Rabah et al, 2007, APHA, 1992, River Watch Network, 1991, USEPA, 1985).…”

Freshwater salmon aquaculture in Chile and transferable antimicrobial resistance

“…The absence of control samples from non-anthropogenically impacted freshwater sources in the present study hinders any conclusion that the presence of aad or other antimicrobial resistance genes in their samples is a result of aquaculture, as their findings could just as easily be due to leakage of these genes from pre-existing non-aquacultural environmental or agricultural soil microbiota (Olaitan and Rolain, 2016;Perry et al, 2016;Surette and Wright, 2017). Aquatic antimicrobial-producing Streptomyces as a potential source of aminoglycoside resistance genes certainly exist (Hotta et al, 1980;Davies and Wright, 1997;Rather, 1998;Rabeh et al, 2007;Davies and Davies, 2010), and aad-mediated streptomycin resistance was reported to be widely present in integrons of bacteria from the marine environment nearly 20 years ago despite the lack of veterinary use of this compound for treatment of piscine diseases at that time (L' Abée-Lund and Sørum, 2001). Domínguez et al (2019) provide little molecular evidence to support their hypothesis, such as by demonstrating the presence of DNA sequence-identical clinical integrase genes and/or DNA sequences present in clinical integrons (e.g.…”

Seasonal distribution and activity of nitrogen-cycling bacteria in Bardawil Lagoon, Egypt

“…Complete mixing assists in keeping the water column oxygenated and thus accelerates the decay of organic matter. Because of its shallowness, the relatively poor renewal of the water from the sea and the very high rates of evaporation (Siliem 1989), the lagoon is considered hypersaline (Rabeh et al 2007).…”