In vitro and in vivo sulfate reduction in the gut contents of the termite Mastotermes darwiniensis and the rose-chafer Pachnoda marginata

Sulfate-reducing bacteria (SRB) from termites have been assigned to the genus Desulfovibrio. Desulfovibrio intestinalis lives in the gut of the Australian termite Mastotermes darwiniensis. For the first time we were able to enrich and identify a sulfate-reducing bacterium from the gut of the rose-chafer Pachnoda marginata, which showed the highest 16S rDNA sequence identity (93%) to Desulfovibrio intestinalis and Desulfovibrio strain STL1. Compared to Mastotermes darwiniensis (1x10(7) cells of SRB per ml gut contents), sulfate-reducing bacteria occurred in higher numbers in the gut contents of Pachnoda marginata reaching cell titers of up to 2x10(8) cells per ml gut contents. In vitro sulfate reduction rates were determined with SRB from the gut contents of the termite Mastotermes darwiniensis and the beetle Pachnoda marginata. Due to the higher cell titer, the sulfate reduction rate of Pachnoda marginata was 10(4) nmolxh-1xml-1 and therefore, 21 times higher than that of Mastotermes darwiniensis. In addition, we detected in vivo sulfate reduction in Mastotermes darwiniensis, which indicates that sulfate reducers play an active role in the sulfur metabolism in the termite gut.     

Predatory and biocontrol potency of Bdellovibrio bacteriovorus toward phytopathogenic strains of Pantoea sp. and Xanthomonas campestris in the presence of exo-biopolymers: in vitro and in vivo assessments

International Microbiology - Bdellovibrios are predatory bacteria that invade other live Gram-negative bacterial cells for growth and reproduction. They have recently been considered as potential...     

Synthesis and Characterization of a Novel Extracellular Biogenic Manganese Oxide (Bixbyite-like Mn2O3) Nanoparticle by Isolated Acinetobacter sp.

Recently, manganese oxides have been considered in the environmental remediation, MRI diagnosis and drug and pharmaceutical industries. Different numbers of physicochemical and biological methods have been reported for the preparation of nanoscale manganese oxides. Although manganese oxide biogenesis by bacterial species has been recognized as the major Mn-oxidizing agent in nature, in this research, for first time, we demonstrated the process which used to produce bixbyite-like Mn(2)O(3) nanoparticles by isolated aerobic bacterium from Persian Gulf water. The 16SRNA sequencing showed that this isolate belong to a gram-negative Acinetobacter which produced nano Mn-oxide crystal particle. Characterization of complement morphology, size and chemical structure of these particles were determined by TEM, SEM, EDAX, XRD and FTIR. The data showed that this bacterium could produce nanosized extracellular bixbyite-like Mn(2)O(3) which depend on enzymatic pathway.     

The effect of bacterial glutathione S-transferase on morpholine degradation

Glutathione S-transferases (GSTs) constitute a large family of enzymes that catalyze the addition of glutathione to endogenous, or xenobiotic, often toxic electrophilic compounds. The effect of this enzyme in facilitating polychlorinated biphenyls degradation has been studied previously. Here the effects of induced cell-free extracts of Acinetobacter calcoaceticus and Pseudomonas aeruginosa (grown on hexadecane), and E. coli BL21 (induced with pGEX-2T plasmid on isothiopropylgalactoside) were recruited to facilitate morpholine degradation by Mycobacterium and were compared with non-induced strains. The results showed that all induced strains had significantly more GST activity compared to non-induced ones, and the strain with most GST activity, A. calcoaceticus BS, removed morpholine faster. Eukaryotic GST gene expressed in E. coli BL21 also could facilitate morpholine degradation by Mycobacterium, The same experiments performed with cell-free extracts of non-induced cells did not show any significant effects on morpholine removal. These results showed that there is a correlation between GST activity and acceleration of morpholine degradation.     

Investigation of alkane biodegradation using the microtiter plate method and correlation between biofilm formation, biosurfactant production and crude oil biodegradation

Among 25 crude oil-degrading bacteria isolated from a marine environment, four strains, which grew well on crude oil, were selected for more study. All the four isolated had maximum growth on 2.5% of crude oil and strain BC (Pseudomonas) could remove crude oil by 83%. The drop collapse method and microtiter assay show that this strain produces more biosurfactant, and its biofilm formation is higher compared to other strains. Bacterial adhesions to crude oil for strains CS-2 (Pseudomonas), BC, PG-5 (Rhodococcus) and H (Bacillus) were 30%, 46%, 10% and 1%, respectively. Therefore, strain H with a low production of biosurfactant and biofilm formation had showed the least growth on these compounds. PCR analysis of these four strains showed that all isolates had alk-B genes from group (III) alkane hydroxylase. All isolate strains could utilize cyclohexan, octane, hexadecane, octadecan and diesel fuel oil; however, the microtiter plate assay showed that strain BC had more growth, respiration and biofilm formation on octadecan.     

Effects of boron and calcium supplementation on mechanical properties of bone in rats

OBJECTIVE: The objective of this study was to consider the effects of boron (B) and calcium (Ca) supplementation on mechanical properties of bone tissues and mineral content of the selected bones in rats. METHODS: Adult male Sprague Dawley rats underwent three different treatments with boron and calcium in their drinking water, while taking diet ad libitum for 4 weeks. Rats in the three treatment groups received 2 mg B/d, 300 mg Ca/d, and a combination of 2 mg B+ 300 mg Ca/d, respectively. After the experimental period body weights were recorded and bone mechanical properties were determined on the tibiae, femurs, and fifth lumbar vertebral bones and the mineral contents of these bones was calculated as the ash percentage. RESULTS: Better measurement of bone mechanical properties were observed for boron supplementation. The stiffness of the lumbar vertebral bones tended to increase in all groups and was significant for Ca supplementation. The significant maximal load obtained for boron in all bones indicates higher strength and less strength for apparently a high level of calcium, while this negative defect in the case of lumbar vertebral bones was corrected in the presence of boron. Highest mean energy to maximal load was shown with boron supplementation, demonstrating significant values with Ca group, and lower energy for the lumbar vertebral bones in Ca group in comparison with the controls. Less deformation at the yield points was shown in Ca group. There were no significant differences in ash weights among the four groups. CONCLUSIONS: Additional and longer studies are warranted to further determine the effects of supplemental boron with different calcium levels and possibly other minerals involved in bone mechanical properties in rats.     

Novel filamentous spore-forming iron bacteria causes bulking in activated sludge

Several Gram-positive iron bacteria were isolated from bulking sludge. They were filamentous and had false branching. They had sheaths with iron deposits and formed spores on modified sucrose casitone yeast extract agar. They did not grow on influsion agar for longer than 1 month but could withstand 80°C for 1 h on the same medium. Adding them to sewage before aeration increased the biochemical oxygen demand of waste water and caused poor settling properties of activated sludges. They were the predominant filamentous micro-organisms in bulking activated sludges. At present, these strains cannot be assigned to recognized taxa of Bacillus spp. or sheathed iron bacteria.     

Synthesis of new poly(ether–urethane–urea)s based on amino acid cyclopeptide and PEG: study of their environmental degradation

Conventional polyurethanes (PUs) are among biomaterials not intended to degrade but are susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. Biodegradable PUs are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. In this work we have developed a degradable monomer based on α-amino acid to accelerate hard segment degradation. Thus a new class of degradable poly(ether–urethane–urea)s (PEUUs) was synthesized via direct reaction of 4,4′-methylene-bis(4-phenylisocyanate) (MDI), l-leucine anhydride (LA) and polyethylene glycol with molecular weight of 1,000 (PEG-1000) as polyether soft segment. The resulting polymers are environmentally biodegradable and thermally stable. Decomposition temperatures for 5 % weight loss occurred above 300 °C by TGA in nitrogen atmospheres. Some structural characterization and physical properties of these polymers before and after degradation in soil, river water and sludge are reported. The environmental degradation of the polymer films was investigated by SEM, FTIR, TGA, DSC, GPC and XRD techniques. A significant rate of degradation occurred in PEUU samples under river water and sludge condition. The polymeric films were not toxic to E. coli (Gram negative), Staphylococcus aureus and Micrococcus (Gram positive) bacteria and showed good biofilm formation on polymer surface. Our results show that hard segment degraded selectively as much as soft segment and these polymers are susceptible to degradation in soil and water. Thus our study shows that new environment-friendly polyurethane, which can degrade in soil, river water and sludge, is synthesized.