title: Polysaccharide Degradation Capability of Actinomycetales Soil Isolates from a Semiarid Grassland of the Colorado Plateau.
abstract: Among the bacteria, members of the orderActinomycetalesare considered quintessential degraders of complex polysaccharides in soils. However, studies examining complex polysaccharide degradation byActinomycetales(other thanStreptomycesspp.) in soils are limited. Here, we examine the lignocellulolytic and chitinolytic potential of 112Actinomycetalesstrains, encompassing 13 families, isolated from a semiarid grassland of the Colorado Plateau in Utah. Members of theStreptomycetaceae,Pseudonocardiaceae,Micromonosporaceae, andPromicromonosporaceaefamilies exhibited robust activity against carboxymethyl cellulose, xylan, chitin, and pectin substrates (except for low/no pectinase activity by theMicromonosporaceae). When incubated in a hydrated mixture of blendedStipaandHilariagrass biomass over a 5-week period,StreptomycesandSaccharothrix(a member of thePseudonocardiaceae) isolates produced high levels of extracellular enzyme activity, such as endo- and exocellulase, glucosidase, endo- and exoxylosidase, and arabinofuranosidase. These characteristics make them well suited to degrade the cellulose and hemicellulose components of grass cell walls. On the basis of the polysaccharide degradation profiles of the isolates, relative abundance ofActinomycetalessequences in 16S rRNA gene surveys of Colorado Plateau soils, and analysis of genes coding for polysaccharide-degrading enzymes among 237Actinomycetalesgenomes in the CAZy database and 5 genomes from our isolates, we posit thatStreptomycesspp. and select members of thePseudonocardiaceaeandMicromonosporaceaelikely play an important role in the degradation of hemicellulose, cellulose, and chitin substances in dryland soils.IMPORTANCEShifts in the relative abundance ofActinomycetalestaxa have been observed in soil microbial community surveys during large, manipulated climate change field studies. However, our limited understanding of the ecophysiology of diverseActinomycetalestaxa in soil systems undermines attempts to determine the underlying causes of the population shifts or their impact on carbon cycling in soil. This study combines a systematic analysis of the polysaccharide degradation potential of a diverse collection ofActinomycetalesisolates from surface soils of a semiarid grassland with analysis of genomes from five of these isolates and publicly availableActinomycetalesgenomes for genes encoding polysaccharide-active enzymes. The results address an important gap in knowledge ofActinomycetalesecophysiology-identification of key taxa capable of facilitating lignocellulose degradation in dryland soils. Information from this study will benefit future metagenomic studies related to carbon cycling in dryland soils by providing a baseline linkage ofActinomycetalesphylogeny with lignocellulolytic functional potential.
authors.affiliation: Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA cyeager@lanl.gov.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Yeager
authors.affiliation: Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
authors.forename: La Verne
authors.initials: V
authors.lastname: Gallegos-Graves
authors.affiliation: Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
authors.forename: John
authors.initials: J
authors.lastname: Dunbar
authors.affiliation: Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
authors.forename: Cedar N
authors.initials: CN
authors.lastname: Hesse
authors.affiliation: Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
authors.forename: Hajnalka
authors.initials: H
authors.lastname: Daligault
authors.affiliation: Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
authors.forename: Cheryl R
authors.initials: CR
authors.lastname: Kuske
mesh_terms: D000192:Actinomycetales / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002266:Carboxymethylcellulose Sodium / Q000378:metabolism*; D002686:Chitin / Q000378:metabolism*; D057231:Climate Change; D003120:Colorado; D065948:Grassland; D008031:Lignin / Q000378:metabolism*; D010368:Pectins / Q000378:metabolism*; D010802:Phylogeny; D011134:Polysaccharides / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D014990:Xylans / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; D012336:RNA, Ribosomal, 16S; D012987:Soil; D014990:Xylans; C036909:lignocellulose; D002686:Chitin; D010368:Pectins; D008031:Lignin; D002266:Carboxymethylcellulose Sodium
keywords: Actinomycetales; cellulose; chitin; dryland; pectin; polysaccharide; soil; xylan