Transport of bacteria in porous media: II. A model for convective Transport and growth

A model is presented for the coupled processes of bacterial growth and convective transport of bacteria has been modeled using a fractional flow approach. The various mechanisms of bacteria retention can be incorporated into the model through selection of an appropriate shape of the fractional flow curve. Permeability reduction due to pore plugging by bacteria was simulated using the effective medium theory. In porous media, the rates of transport and growth of bacteria, the generation of metabolic products, and the consumption of nutrients are strongly coupled processes. Consequently, the set of governing conservation equations form a set of coupled, nonlinear partial differential equations that were solved numerically. Reasonably good agreement between the model and experimental data has been obtained indicating that the physical processes incorporated in the model are adequate. The model has been used to predict the in situ transport and growth of bacteria, nutrient consumption, and metabolite production. It can be particularly useful in simulating laboratory experiments and in scaling microbial-enhanced oil recovery or bioremediation processes to the field. (c) 1994 John Wiley & Sons, Inc.     

Temperature Effects on Development and Reproduction of Heterodera cajani on Pigeonpea

Effects of constant and fluctuating temperature on development and reproduction of Heterodera cajani were studied on pigeonpea cv. ICPL 87 in growth chambers at 10, 15, 20, 25, and 30 C and in a greenhouse fluctuating between 22.2 and 37.8 C. Nematode penetration was greatest (P = 0.001) in roots at 25 C; there was no penetration at 10 C. The basal threshold temperature for development was calculated to be 11 C. Completion of one H. cajani generation required 17, 28, 35, and 66 days (323, 392, 315, and 264 degree-days) at 30, 25, 20, and 15 C, respectively, and 19 days (356 degree-days) at a fluctuating temperature. Survival was greater at 20 and 25 C than at 15 and 30 C. The greatest (P = 0.05) number of females (17.9 females per root) were produced at 25 C, compared with 13.2 at 20 C, 7.9 at 30 C, and 2.5 females at 15 C. Nematode reproduction was 1.6 to 7.1 times greater at 25 C than at other temperatures. Emergence of juveniles from egg sacs and cysts was greater at 25 and 30 C than at 15 and 20 C. Equations were developed to predict nematode development rate, cumulative juvenile emergence from egg sacs and cysts, and population increases as influenced by temperature.     

Characterization and Plasmid Profile of Xanthomonas campestris pv. Glycines from Maharashtra, India

Xanthomonas campestris pv. glycines , (Xcg), the causative agent of the bacterial pustule disease of soybean was isolated and characterized. On susceptible soybean the pathogenic isolates displayed characteristic chlorotic lesions around the site of infection within 48 h of inoculation. The pathogenic isolates were found to contain two cryptic plasmids. A smaller plasmid of 1.5 kb and a larger one of size about 25 kb. SDS-PAGE profile of the soluble proteins of the pathogenic isolatess, howed a different pattern compared to that of the non-pathogenic isolates.     

Plasmid elimination from clinical isolates of Echerichia coli by ciprofloxacin and other inhibitors of DNA gyrase

Summary The susceptibility of 50 drug resistant strains of Escherichia coli of human gut was determined against ciprofloxacin, acridine orange (AO) and sodium dodecyl sulphate (SDS). Curing efficacy of these agents were worked out at subminimal inhibitory concentrations. Ciprofloaxacin was found a better curing agent for E coli R-plasmids, eliminating R-factors from 48% of the strains followed by SDS and AO which eliminated 24% and 20% of the drug resistance determinants, respectively. Elimination of R-plasmids was found dependent on the concentrations of curing agents and nature of R-plasmids.     

Inhibition of glucose oxidation in Erwinia herbicola by a high concentration of dissolved O2

Oxidation of glucose to 2,5-diketogluconic acid by Erwinia herbicola was inhibited at 100% dissolved O₂ tension (DOT) relative to air at 1 atm. Gluconic acid accumulation, however, increased under this condition. The negative influence of the high DOT is attributed to a 10-fold decrease in 2-ketogluconate dehydrogenase activity.The authors are with the Department of Biotechnology, Regional Research Laboratory, Canal Road, Jammu Tawi-180001, India     

Evidence for the role of intracellular glutamine level in the regulation of glutamine uptake in the cyanobacteriumAnabaena 7120

The role of intracellular glutamine concentration in the regulation of¹⁴C-glutamine uptake was studied in a diazotrophic cyanobacteriumAnabaena 7120. The uptake pattern was found to be biphasic, consisting of a rapid first phase lasting up to 60 s followed by a slower second phase. Azaserine, which could not inhibit in vitro and in vivo glutamine synthetase (GS) activity effectively, inhibited the¹⁴C-glutamine uptake. Glutamine uptake was also not significantly affected when glutamate, methylglutamate, aspartate, arginine, lysine, hydroxylysine, ornithine, and GS inhibitor,L-methionine-DL-sulfoximine (MSX) were simultaneously available during uptake assay, suggesting that glutamine uptake takes place via a general amino acid permease which does not, however, transport basic and acidic amino acids. The azaserine-treated cells had increased and decreased levels of glutamine and glutamate, respectively, suggesting that the increased intracellular glutamine level is responsible for the inhibition of¹⁴C-glutamine uptake and provides evidence here for the role of an intracellular glutamine pool in the regulation of¹⁴C-glutamine uptake inAnabaena 7120.     

Evaluation of Salmonella Porins as a Broad Spectrum Vaccine Candidate

Porins were prepared from smooth strain of Salmonella typhi 0–901 and chemotype of rough mutant of S. typhimurium Ra-30. Mice were immunized with both the porin preparations in different groups and challenged with S. typhimurium LT2–71 and S. enteritidis SH-1269. Porin immunized mice showed significant protection (P <0.01) against challenge with homologous as well as heterologous strains. Hence, the use of porins may be attempted in future to protect against salmonellosis.     

Production of disease-free encapsulated buds of Zingiber officinale Rosc.

Shoot buds of ginger were successfully encapsulated in 4% sodium alginate gel. Encapsulated buds were germinated in vitro to form roots and shoots. In vitro germination (emergence of sprouts) of encapsulated buds ranged from 16.7% to 81.8% on different media after 5 weeks of incubation. Normal plantlets with an average shoot length of 2.3 cm and 1.7 cm root length were successfully transplanted into unsterilized soil without any hardening process. These plantlets showed no symptoms of ginger yellows disease and the causal fungal pathogen failed to grow out on culture media (used as a diagnostic test).