Identification of denitrifying rhizobacteria from bentgrass and bermudagrass golf greens

AIMS: As high rates of nitrogen fertilization are used in turfgrass management, there is a great potential for nitrogen loss. Research on identification of denitrifiers in turfgrass has been limited. Therefore, the aim was to identify denitrifier species and genes from turfgrass roots. METHODS AND RESULTS: Rhizobacteria were isolated from roots of bentgrass and bermudagrass in sand-based United States Golf Association (USGA) golf greens and used for denitrification biochemical analysis. Seventeen per cent (34 isolates) were identified as denitrifiers, 47% were classified as nitrate-reducers and 36% were nondenitrifiers. Identification of species of the denitrifiers was performed by chromatography fatty acid methyl ester (GC-FAME) and16S rDNA analyses. Bacillus and Pseudomonas were the major turfgrass denitrifiers. The two methods showed a 60% agreement at the genus level. Nitrite reductase genes nirK and nirS were detected in 74 and 15% of the denitrifiers, respectively, but not in nondenitrifiers. The nosZ gene encoding nitrous oxide reductase was detected in all the denitrifiers, but also in some nondenitrifiers. CONCLUSIONS: To our knowledge, this is the first report for identification of denitrifiers and denitrification-related genes associated with turfgrass roots. SIGNIFICANCE AND IMPACT OF THE STUDY: These results provide valuable data for future denitrification studies that seek to improve turfgrass nitrogen management for maximum efficiency.     

Isolation of novel Bacillus species showing high mosquitocidal activity against several mosquito species

Two novel mosquitocidal bacteria, VB17 and VB24, identified as new Bacillus species were isolated from dead mosquito larvae obtained in Florida aquatic habitats. Gas chromatographic analysis of fatty acid methyl esters (GC-FAME) and 16S rRNA sequencing indicated that VB24 is closely related to Bacillus sphaericus whereas VB17 does not have a close relationship with either Bacillus thuringiensis or B. sphaericus. Both isolates were significantly more active than B. sphaericus 2362 against Aedes taeniorhynchus, Anopheles quadrimaculatus, Culex quinquefasciatus larvae, and as active as B. sphaericus 2362 against Anopheles gambiae. Interestingly, however, both were not active against Aedes aegypti larvae, indicating some level of insecticidal specificity.     

Phylogenetic and physiological comparisons of PAH-degrading bacteria from geographically diverse soils

The diversity of bacteria isolated from creosote- contaminated soils in the United States, Norway, and Germany was determined by comparing their ability to degrade polycyclic aromatic hydrocarbons (PAHs), their phospholipid ester-linked fatty acid (GC-FAME) profiles, sole carbon source utilization patterns (Biolog assays (Use of trade names or specific products does not imply endorsement by the U.S. EPA.), and 16S rRNA sequences. Bacteria were initially obtained by enrichment with phenanthrene and fluoranthene. Many were capable of degrading a broad range of the PAHs found in creosote. Phenanthrene- or fluoranthene- degraders were abundant in most of the soils tested. Several of the fluoranthene-degrading isolates clustered with Sphingomonas (formerly Pseudomonas) paucimobilis strain EPA505 in the GC-FAME and Biolog analyses and three of the isolates examined by 16S rRNA sequence comparisons showed a close relationship with Sphingomonas. In addition, the Sphingomonas strains showed the most extensive degradation of 4- & 5-ring PAHs in creosote. Burkholderia cepacia strains isolated on phenanthrene from PAH-contaminated soils had limited ability to attack higher molecular weight PAHs either individually or in creosote. Thus, PAH degradation capabilities appeared to be associated with members of certain taxa, independent of the origin of the soils from which the bacteria were isolated.