The microbial populations in industrial wastewater (rich in ammonia, phenol and
with high salinity) treatments are closely related to Methanobrevibacter smithii, the
predominant methanogen in human intestines (Gomez-Silvan et al. 2010).
The manufacturing of chemical compounds such as pesticides, herbicides and
explosive usually generate effluents containing complex mixtures of salts and nitrate
or nitrite leading to development of resistant to very high nitrate and nitrite concentrations in some species of Haloferax. Hence, it could be useful for bioremediation
applications in sewage plants where high salts, nitrate and nitrite concentrations are
detected in wastewaters and brines. Halophilic archaea, Haloferax mediterranei, are
able to carry out denitrification, thus providing excellent models to explore largescale bioremediation processes to remove nitrogen compounds from brines and salty
water. Similarly, a group of marine bacterial oxidoreductases represented by the
laccases have been studied by metagenomic approach from a marine library. Bacterial laccases are the enzymes which are able to catalyse the oxidation of phenolic and
non-phenolic aromatic compounds and have unusual properties such as high stability
at 40
C, for pHs ranging from 5.5 to 9.0, high activity in the presence of chloride
and high decolourization capability towards azo dyes (Fang et al. 2012). Hence, such
extremophilic microorganisms producing extremozymes find applications in bioremediation of textile dyes in waste water treatment.
12.6 Further Research for Potential Extremophilic
Microorganisms and Their Scale-Up
A primary hurdle in the study of extremophilic microorganisms particularly belonging to Archaea domain used in bioremediation process is methodological. Several
methodologies have been described to study Archaea with a number of archaeal and
universal amplification primer pairs for archaeal diversity (Bonfa et al. 2011;
Khemili-Talbi et al. 2017; Siles and Margesin 2018; Salam et al. 2017; de Jesus
et al. 2015). As PCR amplifications are prone to biases, they may lead to
overrepresent and underrepresent various microbial community members (Pinto
and Raskin 2012). In recent years, relative read depth analysis of the high throughput
sequencing of a 16S rRNA gene amplification product to provide quantitative
measurement of specific Archaea taxonomic groups and metagenomic sequencing
of unamplified DNA (Fig. 12.4) and quantitative PCR (qPCR) methods are used for
analysis of mixed cultures (Smith and Osborn 2009). Second hurdle in studying
Archaea in bioremediation systems is again methodological. Dose–growth response
analysis is generally used to measure community members that outcompete others at
a given physicochemical conditions on a given niche under energy stress (Valentine
2007). In the last several years, this field has made significant advances, but it is still
developing methodology to identify and isolate the suitable extremophile for using
in a particular bioremediation process.
Extremophiles are not cultivable under conventional laboratory culture conditions, but may offer a wealth of valuable bioproducts, ranging from bioactive small
318
S. Kaushik et al.
with high salinity) treatments are closely related to Methanobrevibacter smithii, the
predominant methanogen in human intestines (Gomez-Silvan et al. 2010).
The manufacturing of chemical compounds such as pesticides, herbicides and
explosive usually generate effluents containing complex mixtures of salts and nitrate
or nitrite leading to development of resistant to very high nitrate and nitrite concentrations in some species of Haloferax. Hence, it could be useful for bioremediation
applications in sewage plants where high salts, nitrate and nitrite concentrations are
detected in wastewaters and brines. Halophilic archaea, Haloferax mediterranei, are
able to carry out denitrification, thus providing excellent models to explore largescale bioremediation processes to remove nitrogen compounds from brines and salty
water. Similarly, a group of marine bacterial oxidoreductases represented by the
laccases have been studied by metagenomic approach from a marine library. Bacterial laccases are the enzymes which are able to catalyse the oxidation of phenolic and
non-phenolic aromatic compounds and have unusual properties such as high stability
at 40
C, for pHs ranging from 5.5 to 9.0, high activity in the presence of chloride
and high decolourization capability towards azo dyes (Fang et al. 2012). Hence, such
extremophilic microorganisms producing extremozymes find applications in bioremediation of textile dyes in waste water treatment.
12.6 Further Research for Potential Extremophilic
Microorganisms and Their Scale-Up
A primary hurdle in the study of extremophilic microorganisms particularly belonging to Archaea domain used in bioremediation process is methodological. Several
methodologies have been described to study Archaea with a number of archaeal and
universal amplification primer pairs for archaeal diversity (Bonfa et al. 2011;
Khemili-Talbi et al. 2017; Siles and Margesin 2018; Salam et al. 2017; de Jesus
et al. 2015). As PCR amplifications are prone to biases, they may lead to
overrepresent and underrepresent various microbial community members (Pinto
and Raskin 2012). In recent years, relative read depth analysis of the high throughput
sequencing of a 16S rRNA gene amplification product to provide quantitative
measurement of specific Archaea taxonomic groups and metagenomic sequencing
of unamplified DNA (Fig. 12.4) and quantitative PCR (qPCR) methods are used for
analysis of mixed cultures (Smith and Osborn 2009). Second hurdle in studying
Archaea in bioremediation systems is again methodological. Dose–growth response
analysis is generally used to measure community members that outcompete others at
a given physicochemical conditions on a given niche under energy stress (Valentine
2007). In the last several years, this field has made significant advances, but it is still
developing methodology to identify and isolate the suitable extremophile for using
in a particular bioremediation process.
Extremophiles are not cultivable under conventional laboratory culture conditions, but may offer a wealth of valuable bioproducts, ranging from bioactive small
318
S. Kaushik et al.