title: Influence of long-term land application of Class B biosolids on soil bacterial diversity.
abstract: OBJECTIVE
  To evaluate the effect of long-term annual land applications of Class B biosolids on soil bacterial diversity at University of Arizona Marana Agricultural Field Center, Tucson, Arizona.
  
  
  RESULTS
  Following the final of 20 consecutive years of application of Class B biosolids in March 2005, followed by cotton growth from April to November 2005 surface soil samples (0-30 cm) were collected from control (unamended) and biosolid-amended plots. Total bacterial community DNA was extracted, amplified using 16S rRNA primers, cloned, and sequenced. All 16S rRNA sequences were identified by 16S rRNA sequence analysis and comparison to known sequences in GenBank (NCBI BlastN and Ribosomal Database Project II, RDP). Results showed that the number of known genera (identifiable > 96%) increased in the high rate biosolid plots compared to control plots. Biosolids-amended soils had a broad phylogenetic diversity comprising more than four major phyla: Proteobacteria (32%), Acidobacteria (21%), Actinobacteria (16%), Firmicutes (7%), and Bacteroidetes (6%) which were typical to bacterial diversity found in the unamended arid southwestern soils.
  
  
  CONCLUSIONS
  Bacterial diversity was either enhanced or was not negatively impacted following 20 years of land application of Class B biosolids.
  
  
  CONCLUSIONS
  This study illustrates that long-term land application of biosolids to arid southwestern desert soils has no deleterious effect on soil microbial diversity.
authors.affiliation:  Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, AZ, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zerzghi
authors.affiliation:  USDA-ARS, Genetics and Precision Agriculture Research Unit, Mississippi State, MS, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Brooks
authors.affiliation:  Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, AZ, USA.
authors.forename: C P
authors.initials: CP
authors.lastname: Gerba
authors.affiliation:  Environmental Research Laboratory, The University of Arizona, Tucson, AZ, USA.
authors.forename: I L
authors.initials: IL
authors.lastname: Pepper
mesh_terms: D039903:Actinobacteria / Q000235:genetics / Q000302:isolation & purification; D001130:Arizona; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D044822:Biodiversity; D020560:Proteobacteria / Q000235:genetics / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000009:adverse effects; D012988:Soil Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S; D012722:Sewage