Nitrogen fixation andnif gene organization in branched heterocystous cyanobacteria: Variation in the presence ofxisA

Five branched heterocystous cyanobacteria (Scytonematopsis sp.,Scytonema sp.,Tolypothrix ceylonica, Mastigocladus sp. andFischerella sp.) were examined for their pattern of induction of nitrogenase activity andnif gene organization. All the forms showed the onset of nitrogenase activity after 12 h which could be correlated with the appearance of proheterocysts. The highest activity was exhibited byT. ceylonica. Hybridization studies revealed the presence of thenifD gene but the absence of thexisA gene inMastigocladus sp. andScytonematopsis sp. Interestingly,Tolypothrix sp. andScytonema sp. DNA samples hybridized withxisA. Hence no uniformity seems to exist regarding the presence ofxisA and the relatednif gene organization in branched heterocystous cyanobacteria. This investigation throws light on the primitive character and phylogenetic relatedness of branched forms to the coccoid/colonial forms. It also provides evidence for the proposition that stigonematacean cyanobacteria may not represent the most advanced cyanobacterial forms; rather they may link the coccoid and filamentous forms.     

An invasive Mimosa in India does not adopt the symbionts of its native relatives

Background and Aims

The large monophyletic genus Mimosa comprises approx. 500 species, most of which are native to the New World, with Central Brazil being the main centre of radiation. All Brazilian Mimosa spp. so far examined are nodulated by rhizobia in the betaproteobacterial genus Burkholderia. Approximately 10 Mya, transoceanic dispersal resulted in the Indian subcontinent hosting up to six endemic Mimosa spp. The nodulation ability and rhizobial symbionts of two of these, M. hamata and M. himalayana, both from north-west India, are here examined, and compared with those of M. pudica, an invasive species.

Methods

Nodules were collected from several locations, and examined by light and electron microscopy. Rhizobia isolated from them were characterized in terms of their abilities to nodulate the three Mimosa hosts. The molecular phylogenetic relationships of the rhizobia were determined by analysis of 16S rRNA, nifH and nodA gene sequences.

Key Results

Both native Indian Mimosa spp. nodulated effectively in their respective rhizosphere soils. Based on 16S rRNA, nifH and nodA sequences, their symbionts were identified as belonging to the alphaproteobacterial genus Ensifer, and were closest to the ‘Old World’ Ensifer saheli, E. kostiensis and E. arboris. In contrast, the invasive M. pudica was predominantly nodulated by Betaproteobacteria in the genera Cupriavidus and Burkholderia. All rhizobial strains tested effectively nodulated their original hosts, but the symbionts of the native species could not nodulate M. pudica.

Conclusions

The native Mimosa spp. in India are not nodulated by the Burkholderia symbionts of their South American relatives, but by a unique group of alpha-rhizobial microsymbionts that are closely related to the ‘local’ Old World Ensifer symbionts of other mimosoid legumes in north-west India. They appear not to share symbionts with the invasive M. pudica, symbionts of which are mostly beta-rhizobial.     

Hemodynamic and norepinephrine responses to pacing-induced heart failure in conscious sinoaortic-denervated dogs

Brändle, Marian, Kaushik P. Patel, Wei Wang, andIrving H. Zucker. Hemodynamic and norepinephrine responses topacing-induced heart failure in conscious sinoaortic-denervated dogs.J. Appl. Physiol. 81(4):1855-1862, 1996.The present study was undertaken to determinethe effects of chronic sinoaortic (baroreceptor) denervation (SAD) on the hemodynamic and sympathetic alterations thatoccur in the pacing-induced model of congestive heart failure. Twogroups of dogs were examined: intact(n = 9) and SAD(n = 9). Both groups of dogs werestudied in the control (prepace) state and each week after theinitiation of ventricular pacing at 250 beats/min. After the pacemakerwas turned off, hemodynamic and plasma norepinephrine levels returnedtoward control levels in the prepaced state and after 1 and 2 wk ofpacing. However, by 3 wk all hemodynamic and norepinephrine levelsremained relatively constant over the 10-min observation period withthe pacemaker off. With the pacemaker off, left ventricularend-diastolic pressure went from 2.7 ± 1.4 (SE) mmHg during theprepace state to 23.2 ± 2.9 mmHg in the heart failure state inintact dogs (P < 0.01). Leftventricular end-diastolic pressure increased to 27.1 ± 2.2 mmHgfrom a control level of 4.2 ± 1.9 mmHg in SAD dogs(P < 0.0003). Mean arterial pressuresignificantly decreased in intact and SAD dogs. Resting heart rate wassignificantly higher in SAD dogs and increased to 135.8 ± 8.9 beats/min in intact dogs and 136.1 ± 6.5 beats/min in SAD dogs.There were no significant differences in the hemodynamic parametersbetween intact and SAD dogs after pacing. Plasma norepinephrine wassignificantly lower in intact than in SAD dogs before pacing (197.7 ± 21.6 vs. 320.6 ± 26.6 pg/ml;P < 0.005). In the heart failurestate, plasma norepinephrine increased significantly in both intact(598.3 ± 44.2 pg/ml) and SAD (644.0 ± 64.6 pg/ml) groups. Therewere no differences in the severity or the magnitude of the developedheart failure state in SAD vs. intact dogs. We conclude from these datathat the arterial baroreflex is not the sole mechanism for the increasein sympathetic drive in heart failure.

     

Evaluation of transgenic tobacco plants expressing a bacterial Co-Ni transporter for acquisition of cobalt

Phytoremediation is a viable strategy for management of toxic wastes in a large area/volume with low concentrations of toxic elemental pollutants. With increased industrial use of cobalt and its alloys, it has become a major metal contaminant in soils and water bodies surrounding these industries and mining sites with adverse effects on the biota. A bacterial Co-Ni permease was cloned from Rhodopseudomonas palustris and introduced into Nicotiana tabacum to explore its potential for phytoremediation and was found to be specific for cobalt and nickel. The transgenic plants accumulated more cobalt and nickel as compared to control, whereas no significant difference in accumulation of other divalent ions was observed. The transgenic plants were evaluated for cobalt content and showed increased acquisition of cobalt (up to 5 times) as compared to control. The plants were also assessed for accumulation of nickel and found to accumulate up to 2 times more nickel than control. At the same initial concentration of cobalt and nickel, transgenic plant preferentially accumulated cobalt as compared to nickel. The present study is perhaps the first attempt to develop transgenic plants expressing heterologous Co transporter with an improved capacity to uptake cobalt.     

Effects of arbuscular mycorrhizal fungi and P-solubilizing Pseudomonas fluorescence (ATCC-17400) on morphological traits and mineral content of sesame

Sesame (Sesamum indicum L.) is an important staple crop of the family Pedaliaceae. The commercial production of sesame is still dependent on the applications of chemical fertilizers. Mycorrhiza inoculum resulted in better morphological and biochemical traits in vegetables. Thus, here the outcome of arbuscular mycorrhizal fungi (AMF) and Pseudomonas fluorescence (ATCC-17400) inoculation was studied in the pot culture experiment. Primarily, there seems to be a promising opportunity of AMF in sesame under pot and field trials because of enhanced morphological parameters, especially root weight, and disparities in nutrients and metabolites. The AMF appears to be an option to boost plant growth, mineral content, and sesame yield. The AMF treatment with Pseudomonas fluorescence strain (ATCC-17400) determined the maximum values for the morphological traits and mineral content. Overall, our study highlights mycorrhizal fungi and other microbes efficacy in achieving a successful sesame production.     

Thermal convection over East Antarctica: Potential microorganism dispersal

The Indian Antarctic station, Maitri is in the Schirmacher oasis of east Antarctica. The oasisis covered with snow/ice; except for the local summer season when it gets deglaciated and exposes the small hilly region. During summer, minute microorganisms are observed near water bodies of this rocky terrain. In the year 1996a monostatic acoustic sounder probed planetary boundary layer dynamics over this region. From the data it is observed that the thermal convection (both free and forced) persist for 5.63% of the time in the whole year. The occurrence of free convection predominates in the local summer season around midday, while sporadic cases of forced convection have been recorded during the autumn and winter seasons. The onset of convection is mainly at 0600 hrs to 1200 hrs, while the cessation period is limited within 1400 hrs to 1900 hrs. The cessation of convection is basically governed by the katabatic wind flow around the Schirmacher region and it indicates that the interior of Antarctica or the polar cap ice becomes cooler much faster than the rocky region of Schirmacher oasis.Examples taken from the literatures on atmospheric structure and their effects on dispersal of microorganisms and their distribution by the wind are discussed. The study of monostatic acoustic sounder for thermal convections/plumes may form input for the study of dispersal, survival, metabolicactivities and dispersion model of microorganisms. The application of convection/plume to aerobiology can also lead to improvements in forecasting, monitoring and understanding the various mechanisms of organism dispersal.     

Iron oxide nanoparticles-chitosan composite based glucose biosensor

Iron oxide (Fe(3)O(4)) nanoparticles prepared using co-precipitation method have been dispersed in chitosan (CH) solution to fabricate nanocomposite film on indium-tin oxide (ITO) glass plate. Glucose oxidase (GOx) has been immobilized onto this CH-Fe(3)O(4) nanocomposite film via physical adsorption. The size of the Fe(3)O(4) nanoparticles estimated using X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) has been found to be approximately 22 nm. The CH-Fe(3)O(4) nanocomposite film and GOx/CH-Fe(3)O(4)/ITO bioelectrode have been characterized using UV-visible and Fourier transform infrared (FTIR) spectroscopic and scanning electron microscopy (SEM) techniques, respectively. This GOx/CH-Fe(3)O(4)/ITO nanocomposite bioelectrode has response time of 5s, linearity as 10-400 mgdL(-1) of glucose, sensitivity as 9.3 microA/(mgdLcm(2)) and shelf life of about 8 weeks under refrigerated conditions. The value of Michaelis-Menten (K(m)) constant obtained as 0.141 mM indicates high affinity of immobilized GOx towards the substrate (glucose).     

The role of hepatic, renal and intestinal gluconeogenic enzymes in glucose homeostasis of juvenile rainbow trout

Rainbow trout is unable to utilize high levels of dietary carbohydrates and experiences hyperglycemia after consumption of carbohydrate-rich meals. Carbohydrates stimulate hepatic glycolytic activity, but gene expression of the rate-limiting gluconeogenic enzymes glucose-6-phosphatase (G6Pase), fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase (PEPCK) remains high. Although there is significant mRNA expression and activity of gluconeogenic enzymes in trout intestine and kidney, the regulation of these enzymes by diet is not known. We tested the hypothesis that dietary carbohydrate modulates intestinal and renal G6Pase, FBPase and PEPCK. Fish were either fasted or fed isocaloric carbohydrate-free (CF) or high carbohydrate (HC) diets for 14 days. As expected, fish fed HC exhibited postprandial hyperglycemia and enhanced levels of hepatic glucokinase mRNA and activity. Dietary carbohydrates had no significant effect on the expression and activity of PEPCK, FBPase and G6Pase in all three organs. In contrast, fasting enhanced the activity, but not the mRNA expression of both hepatic and intestinal PEPCK, as well as intestinal FBPase. Therefore, the activity of rate-limiting gluconeogenic enzymes in trout can be modified by fasting, but not by the carbohydrate content of the diet, potentially causing hyperglycemia when fed high levels of dietary carbohydrates. In this species consuming low carbohydrate diets at infrequent intervals in the wild, fasting-induced increases in hepatic and intestinal gluconeogenic enzyme activities may be a key adaptation to prevent perturbations in blood glucose during food deprivation. Presented in part at Experimental Biology, April 2006, San Francisco, CA [Kirchner S., Panserat S., Kaushik S. and Ferraris R. FASEB-IUPS-2006 A667.6].     

Phytochemical and pharmacological studies in <Emphasis Type="Italic">Pedalium murex</Emphasis> L.

Pedalium murex (Pedaliaceae), commonly called Large Caltrops, is known for its pharmacological uses in traditional medicine system. It is reported to have excellent medicinal properties that helps cure reproductive disorders, mainly impotency in men, nocturnal emissions, gonorrhea as well as leucorrhoea in women. Apart from that, it also contains remedy for urinary and gastrointestinal tract disorders. Pharmacologically, the plant has been investigated for antiulcerogenic, nephroprotective, hypolipidemic, aphrodisiac, anti-inflammatory, antidermatophytic, antioxidant, antimicrobial and insecticidal activities. The present review is a bundle of information collected from the published research articles and highlights the phytochemical and pharmacological aspects of P. murex. The information will be helpful in developing the new formulation with therapeutic and economical value in the future.