Microbial communities in pesticide-contaminated soils in Kyrgyzstan and bioremediation possibilities
Microbial communities in pesticide-contaminated soils in Kyrgyzstan and bioremediation possibilities
Tinatin Doolotkeldieva 0 1
Maxabat Konurbaeva 0 1
Saykal Bobusheva 0 1
0 Plant Protection Department, Kyrgyz-Turkish Manas University , 56 Prospect Mira, Bishkek , Kyrgyzstan
1 Responsible editor: Robert Duran
2 Tinatin Doolotkeldieva
In Kyrgyzstan, many former storehouses and dump sites for obsolete pesticides exist. In 2009/2010, an inventory and assessment of these sites including risks of environmental hazard has been conducted by FAO and the World Bank. Monitoring revealed high concentration of pesticides listed as persistent organic pollutants (POPs). The purpose of this research was to study the microbial structural complexes of the pesticide-contaminated soils in these dumping zones, and to search for and select microorganism's destructors with cytochrome P450 genes for pesticide degradation. Culturedependent and culture-independent approaches were used to determine the taxonomic composition of these bacterial communities. The universal primer set for the 16S ribosomal RNA (rRNA) gene and the specific primer set P450R were used to amplify the cytochrome P450 hydroxylase gene. In soils from Suzak A and B and soils from Balykchy dumping sites, the bacteria from the Actinobacteria phylum (Micrococcus genus) were dominant. These bacteria made up 32-47% of the indigenous local mic roflora; bacteria spec ies from the Pseudomonas genus (Gammaproteobacteria phylum) made up 23% in Suzak, 12% in Balykchy soils. Bacillus species from the Firmicutes phylum were found only in Suzak soils. The 16S rRNA analyses and the specific primer set P450R have revealed bacteria with cytochrome genes which are directly involved in the degradation process of organic carbon compounds. Experiments were carried out to help select active degraders from the bacterial populations isolated and used to
Obsolete pesticide dump; Contaminated soil; Microbial consortia; Bacterial populations with P450 cytochrome genes; active bacteria for aerobic bioremediation of pesticides
-
degrade Aldrin in laboratory. Active bacterial strains from the
Pseudomonas fluorescens and Bacillus polymyxa population
were selected which demonstrated high rates of degradation
activity on Aldrin.
Introduction
Pesticides are widely used in agricultural production to
prevent or reduce losses caused by pests. Over 1 billion pounds of
pesticides are used in the USA each year, and approximately
5.6 billion pounds are used worldwide
(United States
Environmental Protection Agency 2011)
. Estimates
concerning the number of obsolete stocks around the world
range from 300,000 to 500,000 t
(FAO 2014, Pieterse et al.
2015)
.
Classes of organic pesticides include organochlorines,
organophosphates, organometallic compounds, pyrethroids, and
carbamates, among others
(Gilden et al. 2010)
. However, their
chemical structures, along with their incorrect preparation,
application, and storage, may pose a serious toxicity risk to
other organisms, both environmental and human
(Fantke et al.
2012; Pieterse et al. 2015; Torres et al. 2013)
. In the present
age, more than 500 different formulations of pesticides are
used, mainly in agricultural tricks. These formulations are in
general artificially synthesized substances that are
nonbiodegradable and enhance environmental toxicity. These
non-biodegradable compounds persist in agricultural fields
after application. About three million people are intoxicated
per annum as a result of pesticide usage, as reported by the
World Health Organization (WHO)
(Veiga et al. 2006)
.
Kyrgyzstan is a unique country with a rich natural and
agricultural biodiversity in almost every region. However,
there is a large legacy of former storehouses and dumping
zones for obsolete pesticides and wastes from pesticide
production, as is often observed in former Soviet countries
(Toichuev et al. 2017a, b; Vijgen et al. 2013; Amirova and
Weber 2015)
but also occurs in other regions
(Jit et al. 2010;
Wycisk et al. 2013)
. In recent years in Kyrgyzstan (2009,
2010), an inventory and assessment of these dumping zones,
and the risk of environmental hazard that they pose, has been
performed by international organizations (FAO, World Bank)
and related international experts. In the territory of
Kyrgyzstan, 50 storage facilities of obsolete pesticides exist,
which store about 5000 t of these hazardous chemicals. In
many places, the local populations try to dig out obsolete
pesticides for reuse. They pose a serious threat to the people
living there, to livestock, and to the environment
(World Bank
2010; Toichuev et al. 2017b)
.
The pesticide level in the environment determines the dose
and time at which an organism is exposed. Due to the mobility
and persistence of these semi-volatile compounds, they can
represent a hazard for the wider environment and can travel
to remote locations. Hence, their persistence in the
environment leads to a risk for (...truncated)