Date Published: January 14, 2016
Publisher: Springer Berlin Heidelberg
Author(s): Shrinivas S. Jadhav, M. David.
Flubendiamide, as a new class (Phthalic acid diamide) of pesticide with a wide spectrum of activity against lepidopteran pests extensively used alone or in combination with other insecticides in agriculture system to get protection from insect pests. Due to high specificity and limited approach towards non-target organism, the extensive use of this pesticide as an alternate for organophosphate and organochlorine pesticides, causing an eventual increase in environmental pollution. Five flubendiamide-resistant bacterial strains were isolated during the present study from agriculture soil considering previous history of pesticide application. Minimal inhibitory concentration of all the isolates showed strain SSJ1 was most efficient flubendiamide resistant organism. Biochemical tests and molecular sequencing of 16s rRNA was carried out which confirmed the isolate as Chryseobacterium indologenes strain SSJ1. UV–visible spectrophotometer study revealed that 89.06 % initial pesticide was removed by the isolate at optimum temperature of 35 °C and pH 7.0 with 5 days incubation period and is further confirmed by high-performance liquid chromatography (HPLC) analysis. Results of the present study however, suggest strain SSJ1 is most resistant to flubendiamide and can possibly be applied in the bioremediation of flubendiamide contaminated soils.
Pesticides pose wide variety of disturbances in aquatic as well as terrestrial organisms, which include morphological, behavioural or physiological disturbances (Xing et al. 2012; Mansour and Mossa 2011; David et al. 2012). These xenobiotics, however, enter food chain and gain access into humans through biomagnifications (Ellgehausen et al. 1980) thereby affecting physiological activities. Indiscriminate use of these pesticides renders a greater threat to living organisms as well as environmental sustainability. Many studies were undertaken which confirm the neurological, physiological disturbances due to pesticide toxicity (David et al. 2015).
In the present study, an attempt was made to isolate flubendiamide resistant bacteria from contaminated agriculture soils of Dharwad district to study their pesticide degrading capabilities. The soil samples were isolated from sites which had previous history of pesticide application and would add to the isolation of strains with desired resistance towards flubendiamide. Physicochemical analysis of soil showed it was nutrient rich with high organic matter (Table 1). This would imply there is no need for further nutrient fortification for bacterial growth. The soil sample was enriched with flubendiamide in MS media and five bacterial strains were isolated. These strains were named as SSJ1, SSJ2, SSJ3, SSJ4 and SSJ5, respectively. Similar study was carried out by Jayanthi and Srujana (2014) successfully isolated four malathion degrading bacteria out of which, strain Achromobacter xylosoxidans utilised malathion as sole carbon and nitrogen source and could effectively reduce the pesticide concentration to undetectable level within 5 days.Table 1Physicochemical property of the soilParameterSand (%)66.0Silt (%)24.2Clay (%)12.6pHa7.3Water holding capacity (ml g−1 soil)0.61Electrical conductivity (m mhos)230Organic matter (%)b1.44Total nitrogen (%)c0.077NH4+—N (µg g−1 soil)d7.56NO2−—N (µg g−1 soil)e0.39NO3−—N (µg g−1 soil)f0.85a1:1.25 = Soil:Water slurrybWalkley–Black method (Jackson 1971)cMicro-Kjeldhal method (Jackson 1971)dNesslerization method (Jackson 1971)eDiazotization method (Barnes and Folkard 1951)fBrucine method (Ranney and Bartlett 1972)
The development and use of different formulations of pesticides in control of pests of agriculture importance have a nugatory effect on environmental sustainability and majority of these mainly reach non-target sites thus entering into food chain as well. Repeated applications of these pesticides have lead to the inception of resistant microorganisms and these microbes both bacteria as well as fungi can be isolated from these contaminated fields. In this work, flubendiamide resistant bacteria were isolated and tested for their degrading capabilities. Among five effective isolates, strain SSJ1, identified as C. indologenes showed maximum resistance of up to 1000 mg/L flubendiamide and degraded about 89.06 % of initial pesticide in 5 days incubation. HPLC reading are confirmative for this removal of pesticide as there was no peak elevation when compared with standards. Further studies are needed to assess effect of consortia on degradation, as well as some research on possible gene responsible for the degradation.