Biosurfactants produced by Bacillus subtilis A1 and Pseudomonas stutzeri NA3 reduce longevity and fecundity of Anopheles stephensi and show high toxicity against young instars

Anopheles stephensi acts as vector of Plasmodium parasites, which are responsible for malaria in tropical and subtropical areas worldwide. Currently, malaria management is a big challenge due to the presence of insecticide-resistant strains as well as to the development of Plasmodium species highly resistant to major antimalarial drugs. Therefore, the present study focused on biosurfactant produced by two bacteria Bacillus subtilis A1 and Pseudomonas stutzeri NA3, evaluating them for insecticidal applications against malaria mosquitoes. The produced biosurfactants were characterized using FT-IR spectroscopy and gas chromatography-mass spectrometry (GC-MS), which confirmed that biosurfactants had a lipopeptidic nature. Both biosurfactants were tested against larvae and pupae of A. stephensi. LC50 values were 3.58 (larva I), 4.92 (II), 5.73 (III), 7.10 (IV), and 7.99 (pupae) and 2.61 (I), 3.68 (II), 4.48 (III), 5.55 (IV), and 6.99 (pupa) for biosurfactants produced by B. subtilis A1 and P. stutzeri NA3, respectively. Treatments with bacterial surfactants led to various physiological changes including longer pupal duration, shorter adult oviposition period, and reduced longevity and fecundity. To the best of our knowledge, there are really limited reports on the mosquitocidal and physiological effects due to biosurfactant produced by bacterial strains. Overall, the toxic activity of these biosurfactant on all young instars of A. stephensi, as well as their major impact on adult longevity and fecundity, allows their further consideration for the development of insecticides in the fight against malaria mosquitoes

Influence of thermophilic bacteria on corrosion of carbon steel in hyper chloride environment

The present study evaluates, the oxidation behaviour of thermophilic bacteria Geobacillus thermoparaffinivorans IR2, Geobacillus stearothermophillus IR4 and Bacillus licheniformis MN6 on carbon steel API 5 LX by weight loss, electrochemical studies (impedance and polarization analysis) and surface analysis (X-ray diffraction spectroscopy). The presence of IR2, IR4 and MN6 showed highest corrosion rate (CR) of 2.51, 2.82 and 2.41 mm/year, respectively, than the abiotic control (0.95 mm/year). Whereas in the presence of biocide tetrakis (hydroxymethyl) phosphonium sulphate (THPS) inhibition of the biofilm formation was noticed on the carbon steel and thus reduced the CR of about 0.36, 0.46 and 0.42 mm/year. The electrochemical studies also revealed that higher charge transfer resistance (105 Ω cm 2 ) and solution resistance (6.99 Ω cm 2 ) in the presence of THPS due to the intact protective film on carbon steel surface. Thus, THPS is found to act as an effective candidate towards control microbial influenced corrosion by thermophilic bacteria on carbon steel API5LX in a 36% chloride environment