Diversity and distribution of sulfate-reducing bacteria in permanently frozen Lake Fryxell, McMurdo Dry Valleys, Antarctica

The permanently frozen freshwater Lake Fryxell, located in the Dry Valleys of Antarctica, exhibits an ideal geochemistry for microbial sulfate reduction. To investigate the population of sulfate-reducing bacteria in Lake Fryxell, both 16S rRNA gene and metabolic primer sets targeting the dsrA gene for the dissimilatory sulfite reductase alpha subunit were employed to analyze environmental DNA obtained from the water column and sediments of Lake Fryxell. In addition, enrichment cultures of sulfate-reducing bacteria established at 4 degrees C from Lake Fryxell water were also screened using the dsrA primer set. The sequence information obtained showed that a diverse group of sulfate-reducing prokaryotes of the domain Bacteria inhabit Lake Fryxell. With one exception, the enrichment culture sequences were not represented within the environmental sequences. Sequence data were compared with the geochemical profile of Lake Fryxell to identify possible connections between the diversity of sulfate-reducing bacteria and limnological conditions. Several clone groups were highly localized with respect to lake depth and, therefore, experienced specific physiochemical conditions. However, all sulfate-reducing bacteria inhabiting Lake Fryxell must function under the constantly cold conditions characteristic of this extreme environment.     

Malate dehydrogenase in phototrophic purple bacteria: purification, molecular weight, and quaternary structure.

The citric acid cycle enzyme malate dehydrogenase was purified to homogeneity from the nonsulfur purple bacteria Rhodobacter capsulatus, Rhodospirillum rubrum, Rhodomicrobium vannielii, and Rhodocyclus purpureus. Malate dehydrogenase was purified from each species by either a single- or a two-step protocol: triazine dye affinity chromatography was the key step in purification of malate dehydrogenase in all cases. Purification of malate dehydrogenase resulted in a 130- to 240-fold increase in malate dehydrogenase specific activity, depending on the species, with recoveries ranging from 30 to 70%. Homogeneity of malate dehydrogenase preparations from the four organisms was determined by sodium dodecyl sulfate and nondenaturing polyacrylamide gel electrophoresis; a single protein band was observed in purified preparations by both techniques. The molecular weight of native malate dehydrogenases was determined by four independent methods and estimated to be in the range of 130,000 to 140,000 for the enzyme from R. capsulatus, R. rubrum, and R. vannielii and 57,000 for that from R. purpureus. It is concluded that malate dehydrogenase from R. capsulatus, R. rubrum, and R. vannielii is a tetramer composed of four identical subunits, while the enzyme from R. purpureus is a dimer composed of two identical subunits.     

Rapid identification of non-allelic nystatin resistance mutations inDictyostelium discoideum

Spontaneous nystatin resistance mutations inDictyostelium discoideum fall into three complementation groups;nys A. nys B andnys C. We demonstrate three methods for rapidly distinguishing mutations in the three complementation groups. In the first methodnys B andnys C mutations are identified by their sensitivity to the sterol biosynthesis inhibitors azasterol A25822B and fenarimol respectively. The second method exploits the differential sensitivities of thenys mutations to the polyene antibiotic pimaricin. In the last method we show thatnys C and non-nys C mutants can be distinguished on the basis of the Lieberman-Burchard color reaction for sterols.     

Pathophysiology and therapy for haemoglobinopathies. Part II: thalassaemias

Thalassaemias result from mutations of the globin genes that cause reduced or absent haemoglobin production and thus interfere with the critical function of oxygen delivery. They represent the most common single-gene disorders, with 4.83% of the world population carrying globin gene variants. Reduced or absent alpha-globin (alpha-thalassaemia) or beta-globin (beta-thalassaemia) leads to anaemia and multifaceted clinical syndromes. In this second of two reviews on the pathophysiology of haemoglobinopathies, we describe the clinical features, pathophysiology and molecular basis of alpha- and beta-thalassaemias. We then discuss current targeted therapies, including the new oral iron chelators, which, along with chronic transfusions, constitute the mainstay of symptomatic therapy for the majority of patients. Finally, we describe potentially curative therapies, such as bone marrow transplant, and discuss some of the outstanding research studies and questions, including the upcoming field of gene therapy for beta-thalassaemia. An accompanying article on haemoglobinopathies (Part I) focuses on sickle cell disease.     

Production of poly-beta-hydroxyalkanoates from soy molasses oligosaccharides by new, rapidly growing Bacillus species

AIMS: To isolate and characterize bacteria from nature capable of producing poly-beta-hydroxyalkanoates in high yields from soy molasses oligosaccharides. METHODS AND RESULTS: Several strains of bacteria were obtained from enrichment cultures employing raffinose as major carbon source and inoculated with soybean field soil, lake sediment, or lake water. Many of the isolates were Bacillus species and produced polyhydroxyalkanoates (PHAs) to high yield. The raffinose-degrading isolates produced endospores, were highly saccharolytic, and both respired and fermented a variety of mono-, di-, tri- and tetrasaccharides. Strain CL1 produced 90% of cell dry mass as PHA from various sugars, including raffinose, and did so without requiring a nutrient limitation. CONCLUSIONS: Strain CL1 could be the catalyst for an industrial fermentation converting soy molasses and other waste carbohydrates to PHAs. The properties of this organism that make it ideally suited for such a fermentation include (i) its ability to use a wide variety of plant-associated carbohydrates as PHA feedstocks; (ii) its rapid growth; (iii) its ability to grow under anoxic conditions; and (iv) its ability to produce spores. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of bacteria capable of making biodegradable plastics to high yield from soy molasses oligosaccharides.     

Pathophysiology and therapy for haemoglobinopathies. Part I: sickle cell disease

In sickle cell disease, a single base pair substitution in the gene encoding the beta-globin chain of the haemoglobin molecule gives rise to a surprisingly broad spectrum of pathophysiological and clinical manifestations. Inflammation, endothelial activation, red blood cell membrane abnormalities and altered availability of vasoactive factors characterise this disorder. Clinically, patients suffer from a host of seemingly unrelated maladies, from pain episodes to strokes, life-threatening infections and pulmonary hypertension. Deepened understanding of this complex disease now allows us to begin to turn away from simple supportive treatments, and move towards therapies aimed at specific pathophysiological targets. This article, the first of two reviews on the pathophysiology of haemoglobinopathies, discusses the molecular basis of sickle cell disease, and elaborates on the many factors that exacerbate or ameliorate the disease process. It then focuses on the promising targeted therapies currently in use or under investigation. An accompanying article on haemoglobinopathies (Part II) focuses on thalassaemias.     

Photopigments in Rhodopseudomonas capsulata cells grown anaerobically in darkness.

The phototrophic bacterium Rhodopseudomonas capsulata can obtain energy for dark anaerobic growth from sugar fermentations dependent on accessory oxidants such as trimethylamine-N-oxide or dimethyl sulfoxide. Cells grown for one to two subcultures in this fashion, with fructose as the energy source, showed approximately a twofold increase in bacteriochlorophyll content (per milligram of cell protein) and developed extensive intracytoplasmic membranes in comparison with cells grown photosynthetically at saturating light intensity. Cells harvested from successive anaerobic dark subcultures, however, showed progressively lower pigment contents. After ca. 20 transfers, bacteriochlorophyll and carotenoids were barely detectable, and the amount of intracytoplasmic membrane diminished considerably. Spontaneous mutants incapable of producing normal levels of photosynthetic pigments arose during prolonged anaerobic dark growth. Certain mutants of this kind appear to have a selective advantage over wild-type cells under fermentative growth conditions. Of four pigment mutants characterized (two being completely unable to produce bacteriochlorophyll), only one retained the capacity to grow photosynthetically.     

Bacterial and Archaeal Diversity in Sediments of West Lake Bonney,McMurdo Dry Valleys,Antarctica

Bacterial and archaeal diversity was examined in a sediment core from Lake Bonney, Antarctica. Members of the Archaea showed both low abundance and diversity, whereas bacterial diversity was moderately high and some phyla were fairly abundant, even in geologically old samples. Microbial diversity correlated with sample texture and differed in silty and coarse samples.     

Isolation, Characterization, and Ecology of Cold-Active, Chemolithotrophic, Sulfur-Oxidizing Bacteria from Perennially Ice-Covered Lake Fryxell, Antarctica

Novel strains of obligately chemolithoautotrophic, sulfur-oxidizing bacteria have been isolated from various depths of Lake Fryxell, Antarctica. Physiological, morphological, and phylogenetic analyses showed these strains to be related to mesophilic Thiobacillus species, such as T. thioparus. However, the psychrotolerant Antarctic isolates showed an adaptation to cold temperatures and thus should be active in the nearly freezing waters of the lake. Enumeration by most-probable-number analysis in an oxic, thiosulfate-containing medium revealed that the sulfur-oxidizing chemolithotroph population peaks precisely at the oxycline (9.5 m), although viable cells exist well into the anoxic, sulfidic waters of the lake. The sulfur-oxidizing bacteria described here likely play a key role in the biogeochemical cycling of carbon and sulfur in Lake Fryxell.