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Govender S 《Biotechnology letters》2011,33(2):263-271
Phanerochaete chrysoporium morphology and manganese peroxidase (MnP) productivity was characterised in a scalable, modularised 1145 cm3 membrane gradostat reactor in response to switching between an enhanced production medium and a nutrient limited feed (50%
C and N reduction). Irrespective of the feed composition used nutrients permeating from the lumen of the ultrafiltration membrane
matrix established nutrient gradients across the immobilised biofilm with distinct primary, stationary and decline growth
phases observed. Severe nutrient C and N limitation did not change the cyclic nature of enzyme production (MnPmax = 189.5 U l−1) but did reduce the overall bioreactor efficiency from 32 to 22 U l−1 day−1. Stress induced secondary metabolism resulted in concomitant cell autolysis causing biomass loss and increased operational
flux after 20 days in the 33 day bioreactor operation cycle. 相似文献
34.
Govender Algasan Shaik Rehana Pillay Balakrishna 《World journal of microbiology & biotechnology》2011,27(5):1217-1224
1,2-dichloroethane (DCA) is a toxic synthetic haloalkane produced annually in excess of 20 billion tons. Five bacterial isolates
capable of complete mineralization of DCA have recently been isolated from wastewater treatment facilities in South Africa.
Pulsed field gel electrophoresis (PFGE) and random amplification of polymorphic DNA (RAPD) analysis were employed in this
study to identify phylogenetic differences between these closely-related bacteria. Analysis of the 16S rDNA sequences of the
selected isolates revealed similarities to previously characterised isolates of Ancylobacter aquaticus. It has been previously
shown that all isolates follow the same catabolic pathway and possess an identical hydrolytic dehalogenase (DhlA) involved
in the initial carbonchlorine bond cleavage. Analysis of homology matrices deduced from RAPD and restriction profiles, constructed
using the GelCompar software package, revealed that although some of the isolates possessed identical profiles using one primer
or restriction endonuclease, differences were observed when a different primer was used. Furthermore, the results obtained
indicate that the previously characterised isolate A. aquaticus AD25 is significantly different from the isolates used in
this study. PFGE was also able to show that isolates of A. aquaticus do not possess the 200 kb plasmid containing the hydrolytic
dehalogenase gene previously identified in the DCA-degrading bacterium Xanthobacter autotrophicus GJ10. This study has been
able to demonstrate that RAPD and PFGE analysis are suitable molecular tools for the differentiation of closely-related A.
aquaticus isolates and may be routinely used in the differentiation of environmentally important bacteria. 相似文献
35.
Kwezi L Ruzvidzo O Wheeler JI Govender K Iacuone S Thompson PE Gehring C Irving HR 《The Journal of biological chemistry》2011,286(25):22580-22588
Phytosulfokines (PSKs) are sulfated pentapeptides that stimulate plant growth and differentiation mediated by the PSK receptor (PSKR1), which is a leucine-rich repeat receptor-like kinase. We identified a putative guanylate cyclase (GC) catalytic center in PSKR1 that is embedded within the kinase domain and hypothesized that the GC works in conjunction with the kinase in downstream PSK signaling. We expressed the recombinant complete kinase (cytoplasmic) domain of AtPSKR1 and show that it has serine/threonine kinase activity using the Ser/Thr peptide 1 as a substrate with an approximate K(m) of 7.5 μm and V(max) of 1800 nmol min(-1) mg(-1) of protein. This same recombinant protein also has GC activity in vitro that is dependent on the presence of either Mg(2+) or Mn(2+). Overexpression of the full-length AtPSKR1 receptor in Arabidopsis leaf protoplasts raised the endogenous basal cGMP levels over 20-fold, indicating that the receptor has GC activity in vivo. In addition, PSK-α itself, but not the non-sulfated backbone, induces rapid increases in cGMP levels in protoplasts. Together these results indicate that the PSKR1 contains dual GC and kinase catalytic activities that operate in vivo and that this receptor constitutes a novel class of enzymes with overlapping catalytic domains. 相似文献
36.
Suhas Ramesh Prabhakar Cherkupally Beatriz G. de la Torre Thavendran Govender Hendrik G. Kruger Fernando Albericio 《Amino acids》2014,46(9):2091-2104
The twenty first century has witnessed several advances in synthetic chemistry, among them microreactors. It is expected that these devices will have a considerable impact on synthetic organic chemistry since they offer a wide range of applications in various fields. Perhaps the synthesis of peptides deserves mention in this regard as these molecules are emerging as therapeutics and offer several advantages over the so-called small molecules. This minireview does not aim to address microreactors in detail, but explains various peptide synthesis methods that involve microfluidic techniques, highlighting the need for further improvement and expansion of microdevices/microreactors. 相似文献
37.
Mitchell JE Chetty S Govender P Pillay M Jaggernath M Kasmar A Ndung'u T Klenerman P Walker BD Kasprowicz VO 《PloS one》2012,7(6):e37920
Monitoring of latent Mycobacterium tuberculosis infection may prevent disease. We tested an ESAT-6 and CFP-10-specific IFN-γ Elispot assay (RD1-Elispot) on 163 HIV-infected individuals living in a TB-endemic setting. An RD1-Elispot was performed every 3 months for a period of 3-21 months. 62% of RD1-Elispot negative individuals were positive by cultured Elispot. Fluctuations in T cell response were observed with rates of change ranging from -150 to +153 spot-forming cells (SFC)/200,000 PBMC in a 3-month period. To validate these responses we used an RD1-specific real time quantitative PCR assay for monokine-induced by IFN-γ (MIG) and IFN-γ inducible protein-10 (IP10) (MIG: r?=?0.6527, p?=?0.0114; IP-10: r?=?0.6967, p?=?0.0056; IP-10+MIG: r?=?0.7055, p?=?0.0048). During follow-up 30 individuals were placed on ARVs and 4 progressed to active TB. Fluctuations in SFC did not correlate with CD4 count, viral load, treatment initiation, or progression to active TB. The RD1-Elispot appears to have limited value in this setting. 相似文献
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Issam Al-Rasady Anesh Govender Saud M. Al-Jufaili 《Environmental Biology of Fishes》2012,93(2):177-184
The reproductive pattern of longnose trevally (Carangoides chrysophrys) in the Arabian Sea, off the coast of Oman, is described. Samples were collected on a monthly base between April 2005 and
September 2006 from two landing sites (ALlakbi and Raysuot). A single peak of the gonadosomatic index (GSI) started from September
and ended in February signalling the spawning period. Values of the relative condition factor (K
n
) were fairly constant throughout the year for both males and females and no significantly difference was found in the average
K
n
values between males and females during sampling period. Male and female lengths-at 50% maturity were 46.90 and 42.08 cm,
respectively and were significantly different. This study thus increases our understanding of the reproductive biology of
an important commercial and artisanal fish species in one of its major distribution areas. 相似文献
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Maya Makatini Thashini Chetty Oluseye K. Onajole Thavendran Govender Patrick Govender Glenn E. M. Maguire Hendrik G. Kruger 《Journal of peptide science》2012,18(2):114-121
The synthesis and NMR elucidation of Ala‐Val‐Pro‐Ile and five novel peptide‐based derivatives are reported. These peptides mimic the natural second mitochondria‐derived activator of caspase (Smac) protein. Purification was achieved using preparative HPLC and the NMR elucidation of all compounds is reported for the first time. A series of overlapping signals were observed in the 1D NMR spectra thus making assignment a difficult task to undertake. The use of 2D NMR techniques with the inclusion of efficient adiabatic symmetrized ROESY proved to be an effective tool in overcoming these difficulties. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
40.
Melinda D. Smith Brian W. van Wilgen Catherine E. Burns Navashni Govender re L. F. Potgieter Sandy Andelman Harry C. Biggs Judith Botha Winston S. W. Trollope 《Journal of Plant Ecology》2013,6(1):71
Aim s: The long-term effects of changing fire regimes on the herbaceous component of savannas are poorly understood but essential for understanding savanna dynamics. We present results from one of the longest running (>44 years) fire experiments in savannas, the experimental burn plots (EBPs), which is located in the Kruger National Park (South Africa) and encompasses four major savanna vegetation types that span broad spatial gradients of rainfall (450–700 mm) and soil fertility.Methods: Herbaceous vegetation was sampled twice in the EBPs using a modified step-point method, once prior to initiation of the experiment (1954) and again after 44–47 years. Different combinations of three fire frequency (1-, 2- and 3-year return intervals) and five season (before the first spring rains, after the first spring rains, mid-summer, late summer and autumn) treatments, as well as a fire exclusion treatment, were applied at the plot level (~7 ha each), with each treatment (n = 12 total) replicated four times at each of the four sites (n = 192 plots total). The effects of long-term alterations to the fire regime on grass community structure and composition were analyzed separately for each site.Important Findings: Over the 44+ years duration of the experiment, fires were consistently more intense on sites with higher mean annual rainfall (>570 mm), whereas fires were not as intense or consistent for sites with lower and more variable rainfall (<510 mm) and potentially higher herbivory due to greater soil fertility. Because the plots were open to grazing, the impacts of herbivory along with more variable rainfall regimes likely minimized the effects of fire for the more arid sites. As a consequence, fire effects on grass community structure and composition were most marked for the higher rainfall sites and generally not significant for the more arid sites. For the high-rainfall sites, frequent dry season fires (1- to 3-year return intervals) resulted in high grass richness, evenness and diversity, whereas fire exclusion and growing season fires had the lowest of these measures and diverged the most in composition as the result of increased abundance of a few key grasses. Overall, the long-term cumulative impacts of altered fire regimes varied across broad climatic and fertility gradients, with fire effects on the grass community decreasing in importance and herbivory and climatic variability likely having a greater influence on community structure and composition with increasing aridity and soil fertility. 相似文献