Keywords EndophytesBioremediationNutrient cycling
PhytoremediationBiodegradation
3.1 Introduction
Endophytes are bacterial or fungal microorganisms that colonize healthy plant
tissues intercellular and/or intracellular without causing any apparent symptoms of
disease (Wilson 1995 ). Almost every host plant studied so far is associated with
some microorganism (Arnold et al. 2000 ; Shankar Naik et al. 2008 ). Symbioses
between a fungus and a plant a wide spread phenomenon in nature and plays a
major role in structuring plant communities by affecting colonization, competition,
co-existence and soil nutrient dynamics (Clay and Holah 1999 ; Lemons et al. 2005 ;
Krishnamurthy et al. 2009 ; Ghimire et al. 2010 ; Shankar Naik et al. 2014 ). The
relationship is noted for balanced antagonism between endophytic virulence and
plant defensive response (Schulz and Boyle 2005 ).
Plants have several mechanisms to limit the growth of endophytes including
producing a variety of toxic metabolites (Muciarelli et al. 2007 ; Shankar Naik et al.
2006 ), but over a long period of co-evolution, the host endophyte may develop
genetic systems allowing for the transfer of information themselves. Thus, endo-
phytes have gradually formed a variety of tolerant mechanisms towards host
metabolites by producing exo enzymes and mycotoxins (Costa et al. 2000 ; Schulz
et al. 2002 ). Several workers have reviewed that endophytes produce diverse sec-
ondary metabolites related to terpenes,flavonoides, alkaloids, quinines, cyclohex-
anes and hydrocarbons. Many of these compounds showed antimicrobial,
antioxidant, antineoplastic, anti-leishmanial and anti-proliferative activity, cyto-
toxicity and also fuel production (Shankar Naik et al. 2006 ; Wei et al. 2007 ;
Chomcheon et al. 2009 ; Shankar Naik and Krishnamurthy 2010 ; Wang and Dai
2011 ) (Table3.1). The enzymes produced by endophytic fungi may degrade
macromolecule compounds into small molecules which could allow them to survive
and reproduce despite plant defence mechanisms (Zikmundova et al. 2002 ). The
extra cellular enzymes include pectinase, cellulase, lipoidase proteinase, phenol
oxidase and lignin catabolic enzymes (Oses et al. 2006 ; Tan and Zou 2001 ; Bischoff
et al. 2009 ). Generally fungal endophytes have the ability to utilize various organic
compounds (carbon) which enables them in degradation of structural components
such as glucose, oligosaccharides, cellulose, hemicelluloses, lignin, keratin, pectin,
lipids and proteins (Lumyong et al. 2002 ; Urairaj et al. 2003 ; Tomita 2003 ;
Kudanga and Mwanje 2005 ) present in leaf, litter and wood (Osono and Takeda
2001 ; Urairaj et al. 2003 ). In addition they have potential to decompose environ-
mental pollutants and improve the soil micro environment (Wang and Dai 2011 ).
Few recent studies revealed that endophytes affect litter decomposition rates
(Purahong and Hyde 2011 ) and stimulate soil carbon sequetraton and alter theflux
of greenhouse gases (CO 2 and N 2 O) from soil to the atmosphere (Iqbal et al. 2013 ;
Saikkonen et al 2015 ). With the increasing industrialization of the global economy
48 Y.L. Krishnamurthy and B.S. Naik