Unique Bacteria in Century Old Untreated Or Manure Treated Wheat Soil Ecosystems.

Microorganisms are key players in nutrient cycling and ecosystem functions. Studies were conducted to determine diversity, richness, and uniqueness of bacteria communities in a century-long continuous winter wheat (Triticum aestivum L.) field under manure or chemical fertilizer treatments. Soil samples were obtained from fields of an untreated check (CK), cattle manure addition every four years (M), or nitrogen, phosphorus and potassium (NPK) fertilization every year for over a century.  A total of 12058, 11660, and 10114 sequences of 16S rRNA gene fragments were obtained from CK, M, and NPK, respectively.  A combined total of 21 phyla, 40 classes, 80 orders, 144 families, 355 genus, and 526 species were detected in these three soils.  Of the 21 phyla detected, 12, 13, and 13 phyla were detected in CK, M, and NPK, respectively.  Twelve phyla are common to all systems tested; four phyla are common to both CK and M; two are unique to M; and one is unique to CK. The two unique in M soil are OD1 and Tenericutes; and the one unique to CK is Thermodesulfobacteria.  OD1 is a candidate bacterial phylum that has been widely detected in anaerobic environments, but its metabolisms remain unclear due to lack of cultivated representatives.  Tenericutes is a phylum that contains the class Mollicutes, a group of extremely small bacteria that lack cell wall and have a fluidic shape.  Thermodesulfobacteria is a group of thermophilic sulfate-reducing obligate anaerobes utilizing pyruvate, lactate or H, as electron donors and sulfate or thiosulfate as electron acceptors for growth and sulfide formation.  Thermodesulfobacteria has been reported containing the nitrogen-fixing NifU domain-containing protein.  The ability to fix atmosphere dinitrogen gas is widespread among sulfate-reducing anaerobes.  Our results suggest that cattle manure treatment promoted OD1 and Tenericutes; while century long unfertilization led to detectable dominance of Thermodesulfobacteria.