Microbial Transformation of Xenobiotic Compounds
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Int.J.Curr.Microbiol.App.Sci (2015) 4(4): 429-461 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 4 Number 4 (2015) pp. 429-461 http://www.ijcmas.com Review Article An Environmental Cleanup Strategy - Microbial Transformation of Xenobiotic Compounds Nikki Agrawal* and Ashwini Kumar Dixit Department of Botany, Guru Ghasidas Vishwavidyalaya Koni, Bilaspur (Chhattisgarh) India *Corresponding author ABSTRACT Due to continuous accumulation of recalcitrant xenobiotic compounds into the ecosystem released from various sources caused a serious global concern. K e yw or ds Xenobiotics compounds are carcinogenic, mutagenic, causing teratogenic effect and persist over a long period of time in the environment. Microorganism exhibit Xenobiotics, capability to degrade xenobiotics by their metabolic pathways. Specific catabolic bioremediation, genes are found in a microorganism which are helping in horizontal gene transfer microbial facilitated the rapid microbial transformation of xenobiotic compounds. Molecular- enzymes, biology-based techniques including DNA fingerprinting, microarrays and catabolic genes, metagenomics are used for monitoring and identification of novel bacteria involved horizontal gene in degradation of xenobiotics. These reviews provide an overview of microbial transfer degradation process and catabolic genes, molecular techniques to study the microbial transformation of xenobiotic compounds in modern day technology. Introduction The progress in science, technology and overall damage in ecosystem caused by industries a huge amount of anthropogenic xenobiotic compounds has motivated compounds ranging from raw sewage to researchers to develop new strategies for nuclear wastes is released into the their removal from the contaminated environment. These anthropogenic environment. The application of microbial compounds are xenobiotic compounds technology for the biodegradation of which are toxic to living organisms and xenobiotics from biosphere has received cause a global concern. Xenobiotic much attention. compounds are relatively persisting in the environment because they are highly Xenobiotics are those chemical compounds thermodynamically stable. Xenobiotic that are foreign to a living organism. Human compounds can have various toxic effects on activity creates a lot of recalcitrant humans; they exhibit acute carcinogenic, xenobiotic compounds. According to Sinha mutagenic, and teratogenic effects. The et al. (2009) principal xenobiotics include alkanes, polycyclic aromatic hydrocarbons 429 Int.J.Curr.Microbiol.App.Sci (2015) 4(4): 429-461 (PAHs), antibiotics, synthetic azo dyes, 2008). As reported by Ellis (2003) and pesticides, fuels, solvents, pollutants Tropel and Meer (2004) recent researches (dioxins and polychlorinated biphenyls), are being updated in polyaromatic, chlorinated and nitro-aromatic Biocatalysis/Biodegradation Database, these compounds. The xenobiotic creates a include metabolic pathways of many deleterious effect on the public health. different microorganisms. Bioremediation Xenobiotic compounds e.g. biphenyl can be effective only when environmental compounds, phenols and phthalates work as conditions permit microbial growth and endocrine disruptors (Nagao, 1998; Borgeest activity. Bioremediation involves the et al., 2002). Lindane (HCH) is a neurotoxin manipulation of environmental parameters that interferes with the GABA (pH, temperature, moisture and oxygen) to neurotransmittor function affects the allow microbial growth and degradation nervous system, liver and kidneys. The procedure at a faster rate (Karigar and Rao, overall damage these contaminants have 2011). The development of recombinant motivated scientists to develop strategies for Genetically Modified Organisms (GMOs) is their sequestration and removal from the very significant for the bioremediation of bio-spheres (Saleem et al., 2008). complex waste; through this we can identify the gene responsible for specific compound Biodegradation is a microorganism mediated degradation. transformation of contaminants into non- hazardous or less-hazardous substances The purpose of this review paper is to (Karigar and Rao, 2011). Microorganisms analysis a brief summary of the are nature’s recyclers, converting toxic physiological, genetical and the molecular organic compounds to innocuous approaches for microbial biodegradation of compounds, often carbon dioxide and water certain xenobiotic compounds. (Jain et al., 2005). Vidali (2001) and Leung (2004) reported the appropriate use of Role of microbes in biodegradation various organisms like bacteria, fungi and algae for efficient bioremediation of According to Curtis and Reinhard (1994) pollutants. According to Tropel and Meer microorganisms represent half of the (2004) most organisms, particularly bacteria biomass of our planet. Human activity are known for detoxifying abilities. They disturbs the environment; they introduce mineralize, transform or immobilize the xenobiotic chemicals in the biosphere. pollutants. Bacteria play a crucial role in Microorganism exhibit capability to degrade biogeochemical cycles for sustainable xenobiotics by their metabolic pathways in development of the biosphere. consideration of exploiting as new carbon sources to detoxify toxic compounds The enormous genetic diversity of (Copley, 2000). Microbes show ecofriendly microorganisms, their metabolic plasticity behavior to overcome environmental and high reproduction rates, the capacity for pollution and to help in biodegradation of horizontal gene transfer, ensure the xenobiotic compounds. Microorganisms development and adaptation of apply two modes of action for degradation microorganisms to rapidly changing of xenobiotics compound - 1. Aerobic conditions of the environment (Timmis and biodegradation; 2. Anaerobic Pieper, 1999; Diaz and Prieto, 2000; Kim biodegradation. Aerobic biodegradation and Crowley, 2007; Khomenkov et al., processes require excess O2 delivery 430 Int.J.Curr.Microbiol.App.Sci (2015) 4(4): 429-461 systems, because it is necessary to supply al., 2011; Varsha et al., 2011). Effective continuous O2 due to biofouling in Microorganism (EM) is the consortia of subsurface remedial applications (Baker and valuable microorganisms which secretes Herson, 1994), when bioreactors are applied organic acids and enzymes for utilization its energy costs and sludge production are and degradation of xenobiotic compounds high (McCarty and Smith, 1986; Jewell, (Monica et al., 2011). Microbes are 1987). Anaerobic habitats, including sludge collected from the contaminated sites like digesters, groundwater, sediments, water- waste water, residual sites and distillery laden soils, gastrointestinal contents, feedlot sludges; they are excessively resistance to wastes and landfill sites (Williams, 1977) higher concentrations of xenobionts and some xenobiotic compounds (e.g., (Narasimhulu et al., 2010). Some of toxic tetrachloroethylene, polychlorinated organic pollutants and Heavy metals which biphenyls (PCBs), and nitro-substituted show resistance to some of the microbes can aromatics) can be effectively transformed or be degraded using tolerant microbes mineralized by anaerobic bacteria (Zhang (Tripathi, 2011). For the removal of solid and Bennett, 2005). According to waste effluent activated sludges and aerated Chowdhury et al. (2008) and Varsha et al. lagoons are used they are the richest source (2011) example of aerobic degradative of microbial consortium (Priya et al., 2011). bacteria of xenobiotics are Pseudomonas, Pseudomonas sp. is most efficiently useful Gordonia, Bacillus, Moraxella, in the degradation of xenobiotics such as Micrococcus, Escherichia, Sphingobium, aromatic and aliphatic hydrocarbon of oils. Pandoraea, Rhodococcus,and anaerobic Wasi et al. (2010) reported Pseudomonas xenobiotics degradative bacteria are fluorescens SM1 strain is a good candidate Pelatomaculum, Desulphovibrio, for remediation of some heavy metals and Methanospirillum, Methanosaeta phenolics in heavily polluted sites. Desulfotomaculum, Syntrophobacter, According to Hadad et al. (2005) plastics are Syntrophus. Among them, Pseudomonas manufactured by polyethylenes are degraded species have been the most widely studied by Brevibaccillus borstelensis and due to their dominant performance in Rhodococcus ruber. The scientist has been degrading a wide range of poly cyclic made an attempt to characterize bacterial aromatic compounds from benzene to benzo communities and their responses to (pyrene) (Cao et al., 2009). Overney (1979) xenobiotic pollutants, to isolate potential isolated a Flavobacterium that was able to degraders and to identify the genes involved grow aerobically with the simple model in biodegradation processes (Greene et al., compound 4, 4-dicarboxyazobenzene. 2000; Watanabe et al., 2002). The detailed Pseudomonas desmolyticum NCIM 2112 analysis of microbial diversity, in an exhibit a tremendous capability of environment can be divided into two broad biodegradation of xenobiotic compound categories: culture-dependent studies and (Rokde and Mali, 2013). Many other culture independent studies (Juck et al., bacterial species which assist in degradation 2000). A wide range of unidentified of recalcitrant xenobiotic compounds are pollutant-degrading microorganisms can listed in Table 1. Microbes apply identified by culture independent techniques xenobiotics as their substrates and grow on that can be harbored in contaminated them, degrading or fragmenting them, which environments