Structure of the O-specific polysaccharide from Azospirillum formosense CC-Nfb-7(T).

The lipopolysaccharide was obtained from the cells of Azospirillum formosense CC-Nfb-7(T), a diazotrophic bacterium isolated from agricultural soil. The O-specific polysaccharide (OPS) was released by mild acid hydrolysis of the lipopolysaccharide and was studied by sugar analysis along with 1H and 13C NMR spectroscopy, including 1H,1H COSY, TOCSY, ROESY, 1H,13C HSQC, and HMBC experiments, and Smith degradation. The following structure of partially methylated OPS composed of trisaccharide repeating units was established.

Fluctuation of microbial activities after influent load variations in a full-scale SBR: recovery of the biomass after starvation.

Due to variations in the production levels, a full-scale sequencing batch reactor (SBR) for post-treatment of tannery wastewater was exposed to low and high ammonia load periods. In order to study how these changes affected the N-removal capacity, the microbiology of the reactor was studied by a diverse set of techniques including molecular tools, activity tests, and microbial counts in samples taken along 3 years. The recover capacity of the biomass was also studied in a lab-scale reactor operated with intermittent aeration without feeding for 36 days. The results showed that changes in the feeding negatively affected the nitrifying community, but the nitrogen removal efficiencies could be restored after the concentration stress. Species substitution was observed within the nitrifying bacteria, Nitrosomonas europaea and Nitrobacter predominated initially, and after an ammonia overload period, Nitrosomonas nitrosa and Nitrospira became dominant. Some denitrifiers, with nirS related to Alicycliphilus, Azospirillum, and Marinobacter nirS, persisted during long-term reactor operation, but the community fluctuated both in composition and in abundance. This fluctuating community may better resist the continuous changes in the feeding regime. Our results showed that a nitrifying-denitrifying SBR could be operated with low loads or even without feeding during production shut down periods.

Isolation, characterization and beneficial effects of rice associated plant growth promoting bacteria from Zanzibar soils.

This study was undertaken to isolate and characterize plant growth promoting bacteria (PGPB) occurring in four soils of Zanzibar, Tanzania as well as to evaluate their potential use as biofertilizers for rice. A total of 12 PGPB strains were isolated from rice and studied for growth characteristics, carbon/nitrogen source utilization patterns using QTS-24 kits, phosphate solubilization, indole acetic acid (IAA) production, antibiotic resistance patterns and growth at different pH, temperature and salt concentrations. All the isolates were motile and gram negative except Z3-4. Acetylene reduction activity was detected in all isolates ranging from 5.9-76.4 nmole C2H2 reduced/h x mg protein while 9 isolates produced IAA ranged from 20-90.8 mg/l. Most of the isolates showed resistance against different environmental stresses like 10-40 degrees C temperature, 0.2-1 M salt concentration and 4-8.5 pH range. Only one isolate Z2-7 formed clear zones on Pikovskaia's medium showing its ability to solubilize phosphates. Z3-2 was used to develop fluorescent antibodies to check the cross reactivity of the isolates. Inoculation of these bacterial isolates resulted in higher plant biomass, root area, and total N and P contents on Tanzanian rice variety BKN PRAT3036B under controlled conditions. Bacillus sp. Z3-4 and Azospirillum sp. Z3-1 are effective strains and, after further testing under field conditions, can be used for inoculum production of rice in Tanzania. The plant growth promoting effects of these PGPRs suggest that these can be exploited to improve crop productivity of rice in Tanzania.

Pulsed-field gel electrophoresis fingerprinting for identification of Azospirillum species.

Pulsed-field gel electrophoresis (PFGE) was used to obtain macrorestriction fingerprints of restriction enzyme-cut DNA of natural isolates of Azospirillum spp. Metabolic profiles, along with other phenotypic characteristics, were compared with these fingerprints to differentiate among the azospirilla isolates. A wide diversity of phenotypes (e.g., colony color, motility, and accumulation of poly-beta-hydroxybutyrate granules) was observed among the natural isolates of azospirilla. PFGE revealed that TCTAGA, the sequence recognized by Xba1, is rare in the genome of azospirilla. The PFGE fingerprint revealed that azospirilla associated with different crops have a very similar genetic background. PFGE fingerprints were more consistent in the identification of azospirilla isolates from specific hosts than the metabolic fingerprints. For further differentiation at strain level, metabolic, physiological, and morphological profiles provide additional information.