Heterogeneity in photosystem I. Evidence from cation-induced decrease in Photosystem I electron transport

The rate of electron transfer through Photosystem I (reduced 2,6-dichlorophenol indophenol (DCIPH₂ → methylviologen) in a low-salt thylakoid suspension is inhibited by Mg²⁺ both under light-limited and the light-saturated conditions, the magnitude of inhibition being the same. The 2,6-dichlorophenol indophenol (DCIP) concentration dependence of the light-saturated rate in the presence and in the absence of Mg²⁺ shows that the overall rate constant of the photoreaction is not altered by Mg²⁺. With N,N,N′,N′-tetramethyl-p-phenylenediamine or 2,3,5,6-tetramethylphenylenediamine as electron donor only the light-limited rate, not the light-saturated rate, is inhibited by Mg²⁺ and the magnitude of inhibition is the same as with DCIP as donor. The results are interpreted in terms of heterogeneous Photosystem I, consisting of two types, PS I-A and PS I-B, where PS I-A is involved in cation-regulation of excitation energy distribution and becomes unavailable for DCIPH₂ → methyl viologen photoelectron transfer in the presence of Mg²⁺.     

Synthesis and secretion of cobalamin binding proteins by opossum kidney cells

Opossum kidney epithelial cells synthesize and secrete two Cobalamin (Cbl) binding proteins of Mr 66,000 and 43,000. When grown on culture inserts, the apical medium contained both these proteins while the basolateral medium contained only the 43 kDa Cbl binder. Colchicine, a microtubule disruptive drug, increased two fold the apical but not the basolateral secretion of the Cbl binding proteins. Although the opossum Cbl binders did not cross react with anti-serum raised to Cbl binders from other species, the identity based on Cbl binding and size suggest that the 66 kDa and 43 kDa proteins are haptocorrin and transcobalamin II.     

Renal brush border membrane bound intrinsic factor

A highly active receptor for intrinsic factor (IF)-cobalamin (Cbl) complex has been detected and reported in mammalian kidney earlier (Seetharam, B., et al. (1988) J. Biol. Chem. 263, 4443-4449). The physiological role of this receptor in normal Cbl homeostasis is not known. In addition to binding of exogenously added IF-[57Co]Cbl, the renal apical membranes contain endogenous IF or IF-Cbl. Washing with pH 5/EDTA buffer enhanced the binding of exogenously added IF-[57Co]Cbl to renal apical but not basolateral membranes. The pH 5/EDTA extract from renal apical membranes bound [57Co]Cbl. The complex also bound to rat ileal brush border membrane and promoted ileal transport of [57Co]Cbl. On immunoblots using monospecific antiserum to IF a 62 kDa protein was identified in renal and intestinal apical membranes, serum and in tissue extracts of unperfused rat liver, kidney and heart. The 62 kDa band was eliminated from the renal apical membranes following pH 5/EDTA wash. Rat urine demonstrated unsaturated [57Co]Cbl binding (0.2 to 0.4 pmol/day) of which only 30-40% was immunoprecipitated with anti IF and could be identified on immunoblots. The identification of IF in rat renal apical membranes (160-200 ng/mg protein) and secretion of only traces of IF in urine suggest that the renal IF-Cbl receptor may play a role in sequestering IF/IF-Cbl and prevent urinary loss of Cbl.     

Influence of sowing windows and genotypes on growth,radiation interception,conversion efficiency and yield of guar

Crop growth largely depends on radiation. Radiation is the main impetus for photosynthesis and movement of photosynthates from source to sink. Therefore, identification of the optimum sowing windows and suitable cultivars for efficient utilization of radiation is of prime importance. A field study was conducted in red clay soil during 2014 and 2015 Kharif season and the treatments consisted of three genotypes and three sowing windows by using randomized complete block design with three replications. The effect of genotypes and sowing windows was found significant with respect to number of trifoliate leaves, leaf area ratio, dry matter production, grain numbers, pod length, test weight, grain yield, and stover yield of guar during 2014 as compared to 2015 sown crop. Statistically significant plant height, number of trifoliate leaves, number of branches, leaf area ratio, absolute growth rate, leaf area index, dry matter, grain number, pod length, grain yield, stover yield and a higher cumulative radiation interception were recorded with 15th August sown crop as compared to other sowing windows. The plant height, number of trifoliate leaves, number of branches, leaf area ratio, absolute growth rate, leaf area index, dry matter, grain number, pod length, grain yield, stover yield and maximum cumulative interception of radiation were significant with RGC-1003 as compared to RGC-936 and HG-365. It is observed that the incident PAR to dry matter accumulation conversion efficiency was varied with cultivars and different sowing windows which ranges from 0.74 g MJ⁻¹ to 0.79 g MJ⁻¹.     

Treatment of distillery spentwash by hybrid UASB reactor

A laboratory-scale hybrid UASB reactor, which combined an UASB in the lower part and a filter in the upper part, was used for the treatment of distillery spentwash. The reactor was operated under ambient conditions for 380 days. Using anaerobically digested sewage sludge as a seed, the start-up of the reactor and the cultivation of active granular sludge was completed within three months period. Scanning electron microscopic (SEM) observation of the granules showed the presence of Mehtanonthrix-like bacteria as the dominant species. Following the start-up the organic loading rate (OLR) was increased, stepwise, to 36 kg COD/m³ · d at a constant hydraulic retention time (HRT) of 6 h. COD removal efficiency was 80% even at a high OLR of 36 kg COD/m³ · d. Biogas rich in methane content (80%), with a maximum specific biogas yield of 0.40 m³ CH₄/kg · COD was produced. Polypropylene pall rings filter medium in the upper-third of the reactor was very effective as a gas-liquid-solid (GLS) separator, and retained the biomass in addition. The study indicated that hybrid UASB is a very feasible alternative for the treatment of high-strength wastewaters like distillery spentwash.     

Antibiofilm Activity of Biosurfactant Producing Coral Associated Bacteria Isolated from Gulf of Mannar

Coral Associated Bacteria (CAB) (N = 22) isolated from the mucus of the coral Acropora digitifera were screened for biosurfactants using classical screening methods; hemolysis test, lipase production, oil displacement, drop collapse test and emulsifying activity. Six CAB (U7, U9, U10, U13, U14, and U16) were found to produce biosurfactants and were identified by 16S ribosomal RNA gene sequencing as Providencia rettgeri, Psychrobacter sp., Bacillus flexus, Bacillus anthracis, Psychrobacter sp., and Bacillus pumilus respectively. Their cell surface hydrophobicity was determined by Microbial adhesion to hydrocarbon assay and the biosurfactants produced were extracted and characterized by Fourier Transform Infrared spectroscopy. Since the biosurfactants are known for their surface modifying capabilities, antibiofilm activity of positive isolates was evaluated against biofilm forming Pseudomonas aeruginosa ATCC10145. Stability of the active principle exhibiting antibiofilm activity was tested through various temperature treatments ranging from 60 to 100 °C and Proteinase K treatment. CAB isolates U7 and U9 exhibited stable antibiofilm activity even after exposure to higher temperatures which is promising for the development of novel antifouling agents for diverse industrial applications. Further, this is the first report on biosurfactant production by a coral symbiont.

Electronic supplementary material

The online version of this article (doi:10.1007/s12088-014-0474-8) contains supplementary material, which is available to authorized users.     

Simple cannulation procedure for serial blood sampling through cutaneous ulnar vein in chickens

The objective of the study was to collect repeated, low-stress blood samples from the ulnar vein of chickens required for pharmacokinetic studies or hormonal assays. The study used 5 apparently healthy, unsexed, commercial broiler chickens about 6 weeks old and weighing 1.7-1.9 kg for serial sampling of blood. The study prepared the birds prior to cannulation and penetrated the catheter through the skin and into the lumen of the ulnar vein. The study successfully carried out serial blood samplings in 4 of 5 cannulated birds. Heparin (10%) solution maintained patency and prevented blood clot formation inside the cannula. However, the study found repeated clotting occurring in 1 bird. Cannula failed to maintain patency; the study could not carry out blood sampling properly, which was attributed to air embolism that might have occurred during catheter manipulation or repeated filling of cannula with heparin solution. The study observed no hematoma or inflammation at the site of cannulation. Owing to the advantages and to facilitate compliance with nonhuman animal welfare, this technique seems simple and efficient, allowing adoption for serial blood collection in chickens.     

Mycobacterium tuberculosis and Escherichia coli nucleoside diphosphate kinases lack multifunctional activities to process uracil containing DNA

E. coli nucleoside diphosphate kinase (EcoNDK) is an important cellular enzyme required to maintain balanced nucleotide pools in the cells. Recently, it was reported that EcoNDK is also a multifunctional base excision repair enzyme, possessing uracil-DNA glycosylase (UDG) and AP-DNA processing activities. We investigated for the presence of such activities in M. tuberculosis NDK (MtuNDK), which shares 45.2% identity, and 52.6% similarity with EcoNDK. In contrast to the robust uracil excision activity reported for EcoNDK, MtuNDK preparation exhibited very poor excision of uracil from DNA. However, this activity was undetectable when MtuNDK was purified from an ung(-) strain of E. coli, or when the assays were performed in the presence of extremely low amounts of a highly specific proteinaceous inhibitor, Ugi which forms an extremely tight complex with the host Ung (UDG), showing that MtuNDK preparation was contaminated with UDG. Reinvestigation of uracil processing activity of EcoNDK, showed that even this protein lacked UDG activity. All preparations of NDK were shown to be active by their autophosphorylation activity. Ugi neither displayed a physical interaction with EcoNDK nor did it affect autophosphorylation of NDKs. Further, neither of the NDK preparations processed the AP-DNA generated by UDG treatment of the uracil containing DNA duplexes. However, partially purified preparations of NDK did process such DNA substrates.