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1.
Positive selection is a general phenomenon in the evolution of abalone sperm lysin 总被引:36,自引:21,他引:15
Lysin is a 16kDa acrosomal protein used by abalone sperm to create a hole
in the egg vitelline envelope (VE). The interaction of lysin with the VE is
species-selective and is one step in the multistep fertilization process
that restricts heterospecific (cross-species) fertilization. For this
reason, the evolution of lysin could play a role in establishing prezygotic
reproductive isolation between species. Previously, we sequenced sperm
lysin cDNAs from seven California abalone species and showed that positive
Darwinian selection promotes their divergence. In this paper an additional
13 lysin sequences are presented representing species from Japan, Taiwan,
Australia, New Zealand, South Africa, and Europe. The total of 20 sequences
represents the most extensive analysis of a fertilization protein to date.
The phylogenetic analysis divides the sequences into two major clades, one
composed of species from the northern Pacific (California and Japan) and
the other composed of species from other parts of the world. Analysis of
nucleotide substitution demonstrates that positive selection is a general
process in the evolution of this fertilization protein. Analysis of
nucleotide and codon usage bias shows that neither parameter can account
for the robust data supporting positive selection. The selection pressure
responsible for the positive selection on lysin remains unknown.
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2.
Microbial adaptation to iron: a possible role of phosphatidylethanolamine in iron mineral deposition
Pseudomonas fluorescens multiplied in a minimal mineral medium supplemented with iron(III) (5 mm) complexed to citrate, the sole source of carbon, with no apparent diminution in cellular mass. Atomic absorption studies of different cellular fractions and supernatant at various growth intervals revealed that the trivalent metal was initially internalized. At approximately 41 h of incubation, the soluble cellular extract contained 9.5% of the iron originally found in the growth medium. However, as bacterial multiplication progressed, most of the metal was deposited as an extracellular insoluble gelatinous residue. Phosphatidylethanolamine appeared to be an important organic constituent of this precipitate. X-ray fluorescence and diffraction studies revealed that iron(III) was deposited as amorphous hydrated oxide. Scanning electron microscopy and energy dispersive X-ray microanalysis of the pellet aided in the identification of irregular shaped bodies rich in iron and oxygen that were associated with carbon-containing elongated structures. Examination of the bacterial cells by a transmission electron microscope equipped with an electron energy loss spectrometer indicated the deposition of iron within the cells. 相似文献
3.
Biodeterioration of crude oil and oil derived products: a review 总被引:2,自引:0,他引:2
Natalia A. Yemashova Valentina P. Murygina Dmitry V. Zhukov Arpenik A. Zakharyantz Marina A. Gladchenko Vasu Appanna Sergey V. Kalyuzhnyi 《Reviews in Environmental Science and Biotechnology》2007,6(4):315-337
Biodeterioration of crude oil and oil fuels is a serious economic and an environmental problem all over the world. It is impossible
to prevent penetration of microorganisms in oil and fuels both stored in tanks or in oilfields after drilling. Both aerobic
and anaerobic microorganisms tend to colonise oil pipelines and oil and fuel storage installations. Complex microbial communities
consisting of both hydrocarbon oxidizing microorganisms and bacteria using the metabolites of the former form an ecological
niche where they thrive. The accumulation of water at the bottom of storage tanks and in oil pipelines is a primary prerequisite
for development of microorganisms in fuels and oil and their subsequent biological fouling. Ability of microorganisms to grow
both in a water phase and on inter-phase of water/hydrocarbon as well as the generation of products of their metabolism worsen
the physical and chemical properties of oils and fuels. This activity also increases the amount of suspended solids, leads
to the formation of slimes and creates a variety of operational problems. Nowadays various test-systems are utilized for microbial
monitoring in crude oils and fuels; thus allowing an express determination of both the species and the quantities of microorganisms
present. To suppress microbial growth in oils and fuels, both physico-mechanical and chemical methods are applied. Among chemical
methods, the preference is given to substances such as biocides, additives, the anti-freezing agents etc that do not deteriorate
the quality of oil and fuels and are environmentally friendly. This review is devoted to the analysis of the present knowledge
in the field of microbial fouling of crude oils and oil products. The methods utilized for monitoring of microbial contamination
and prevention of their undesirable activities are also evaluated. The special focus is given to Russian scientific literature
devoted to crude oil and oil products biodeterioration. 相似文献
4.
Zachary Castonguay Christopher AugerSean C. Thomas M’hamed ChahmaVasu D. Appanna 《Biochemical and biophysical research communications》2014
It is becoming increasingly apparent that the nucleus harbors metabolic enzymes that affect genetic transforming events. Here, we describe a nuclear isoform of lactate dehydrogenase (nLDH) and its ability to orchestrate histone deacetylation by controlling the availability of nicotinamide adenine dinucleotide (NAD+), a key ingredient of the sirtuin-1 (SIRT1) deacetylase system. There was an increase in the expression of nLDH concomitant with the presence of hydrogen peroxide (H2O2) in the culture medium. Under oxidative stress, the NAD+ generated by nLDH resulted in the enhanced deacetylation of histones compared to the control hepatocytes despite no discernable change in the levels of SIRT1. There appeared to be an intimate association between nLDH and SIRT1 as these two enzymes co-immunoprecipitated. The ability of nLDH to regulate epigenetic modifications by manipulating NAD+ reveals an intricate link between metabolism and the processing of genetic information. 相似文献
5.
Middaugh J Hamel R Jean-Baptiste G Beriault R Chenier D Appanna VD 《The Journal of biological chemistry》2005,280(5):3159-3165
6.
Oxidized nicotinamide adenine dinucleotide (NAD(+)) kinase (NADK, E.C. 2.7.1.23) plays an instrumental role in cellular metabolism. Here we report on a blue native polyacrylamide gel electrophoretic technique that allows the facile detection of this enzyme. The product, oxidized nicotinamide adenine dinucleotide phosphate (NADP(+)), formed following the reaction of NADK with NAD(+) and adenosine 5'-triphosphate was detected with the aid of glucose-6-phosphate dehydrogenase or NADP(+)-isocitrate dehydrogenase, iodonitrotetrazolium chloride, and phenazine methosulfate. The bands at the respective activity sites were excised and subjected to native and denaturing two-dimensional electrophoresis for the determination of protein levels. Hence this novel electrophoretic method allows the easy detection of NADK, a critical enzyme involved in pyridine homeostasis. Furthermore, this technique allowed the monitoring of the activity and expression of this kinase in various biological systems. 相似文献
7.
Mailloux RJ Lemire J Kalyuzhnyi S Appanna V 《Extremophiles : life under extreme conditions》2008,12(3):451-459
Aluminum (Al), an environmental toxin, is known to have a negative impact on various biological systems. However, some microbes
have devised intricate mechanisms to combat the toxic influence of this trivalent metal. In this study, Pseudomonas fluorescens grown in malate invoked a unique metabolic shift to promote the synthesis of citrate, a metabolite involved in the sequestration
of Al. Electrophoretic and spectrophotometric assays revealed several malate-metabolizing enzymes including malate dehydrogenase
(MDH) and malic enzyme (ME) displayed increases in activity and expression in the Al-treated cells. Whereas pyruvate dehydrogenase
(PDH) also showed increased activity and expression in the Al-stressed cultures, phosphoenolpyruvate carboxykinase (PEPCK)
displayed a marked diminution in the Al-treated cells. The upregulation of citrate synthase (CS) coupled with the diminished
activities of aconitase (ACN) and NAD-isocitrate dehydrogenase (NAD-ICDH) appeared to be instrumental in the accumulation
of citrate. HPLC experiments revealed high levels of citrate in the Al-stressed cultures. Thus, an Al-enriched environment
provoked a metabolic shift in P. fluorescens dedicated to the conversion of malate to citrate. 相似文献
8.
Aluminum (Al), a known environmental pollutant, has been linked to numerous pathologies such as Alzheimer's disease and anaemia. In this study, we show that α-ketoglutarate (KG) mitigates the Al-mediated nuclear accumulation of hypoxia inducible factor-1α (HIF-1α) in cultured human hepatocytes (HepG2). The nuclear localization of HIF-1α appeared to be triggered by the Al-induced perturbation of prolyl hydroxylase 2 (PHD2). This enzyme was markedly diminished in the Al-challenged hepatocytes. The fate of PHD2 and HIF-1α was intricately linked to the mitochondrial dysfunction observed during Al stress. BN-PAGE, immunoblot, and HPLC revealed that the loss of α-ketoglutarate dehydrogenase (KGDH) and succinate dehydrogenase (SDH) activities were coupled to the accumulation of succinate. However, the treatment of the Al-stressed cells with KG recovered the activity and expression of KGDH, SDH, and PHD2 with a concomitant decrease in the levels of HIF-1α in the nucleus. Taken together, these data indicate that the homeostasis of KG plays a pivotal role in aerobic and anaerobic respiration. 相似文献
9.
Ranji Singh Joseph Lemire Ryan J. Mailloux Daniel Chénier Robert Hamel Vasu D. Appanna 《PloS one》2009,4(10)
Although the tricarboxylic acid (TCA) cycle is essential in almost all aerobic organisms, its precise modulation and integration in global cellular metabolism is not fully understood. Here, we report on an alternative TCA cycle uniquely aimed at generating ATP and oxalate, two metabolites critical for the survival of Pseudomonas fluorescens. The upregulation of isocitrate lyase (ICL) and acylating glyoxylate dehydrogenase (AGODH) led to the enhanced synthesis of oxalate, a dicarboxylic acid involved in the immobilization of aluminum (Al). The increased activity of succinyl-CoA synthetase (SCS) and oxalate CoA-transferase (OCT) in the Al-stressed cells afforded an effective route to ATP synthesis from oxalyl-CoA via substrate level phosphorylation. This modified TCA cycle with diminished efficacy in NADH production and decreased CO2-evolving capacity, orchestrates the synthesis of oxalate, NADPH, and ATP, ingredients pivotal to the survival of P. fluorescens in an Al environment. The channeling of succinyl-CoA towards ATP formation may be an important function of the TCA cycle during anaerobiosis, Fe starvation and O2-limited conditions. 相似文献
10.