Complementary Functioning of Nitrogenase Components from a Blue-Green Alga and a Photosynthetic Bacterium

Nitrogenases from Anabaena cylindrica and Chloropseudomonas ethylicum were partially purified into two components. A. cylindrica fraction I protein complemented fraction II protein from C. ethylicum. However, the reciprocal cross between C. ethylicum fraction I and A. cylindrica fraction II was negative.     

Mobility of Nuclear Components and Genome Functioning

Cell nucleus is characterized by strong compartmentalization of structural components in its three-dimensional space. Certain genomic functions are accompanied by changes in the localization of chromatin loci and nuclear bodies. Here we review recent data on the mobility of nuclear components and the role of this mobility in genome functioning.     

Community Composition and Functioning of Denitrifying Bacteria from Adjacent Meadow and Forest Soils

We investigated communities of denitrifying bacteria from adjacent meadow and forest soils. Our objectives were to explore spatial gradients in denitrifier communities from meadow to forest, examine whether community composition was related to ecological properties (such as vegetation type and process rates), and determine phylogenetic relationships among denitrifiers. nosZ, a key gene in the denitrification pathway for nitrous oxide reductase, served as a marker for denitrifying bacteria. Denitrifying enzyme activity (DEA) was measured as a proxy for function. Other variables, such as nitrification potential and soil C/N ratio, were also measured. Soil samples were taken along transects that spanned meadow-forest boundaries at two sites in the H. J. Andrews Experimental Forest in the Western Cascade Mountains of Oregon. Results indicated strong functional and structural community differences between the meadow and forest soils. Levels of DEA were an order of magnitude higher in the meadow soils. Denitrifying community composition was related to process rates and vegetation type as determined on the basis of multivariate analyses of nosZ terminal restriction fragment length polymorphism profiles. Denitrifier communities formed distinct groups according to vegetation type and site. Screening 225 nosZ clones yielded 47 unique denitrifying genotypes; the most dominant genotype occurred 31 times, and half the genotypes occurred once. Several dominant and less-dominant denitrifying genotypes were more characteristic of either meadow or forest soils. The majority of nosZ fragments sequenced from meadow or forest soils were most similar to nosZ from the Rhizobiaceae group in α-Proteobacteria species. Denitrifying community composition, as well as environmental factors, may contribute to the variability of denitrification rates in these systems.     

Characterization of Two Extracellular Polysaccharides from Marine Bacteria

Two bacterial isolates from the intertidal zone produced significant quantities of extracellular polysaccharide with interesting properties. One polysaccharide was named PS 3a24; the other was named PS 3a35. The relative proportion of sugars in PS 3a35 was 51.6% glucose, 39.0% galactose, 3.1% mannose, and 6.3% rhamnose, with a trace of an unidentified sugar. PS 3a24 was composed of 40.2% glucose, 57.2% galactose, and 2.6% mannose. PS 3a35 contained 6% pyruvate, whereas PS 3a24 contained no pyruvate. Both exhibited high specific viscosity, pseudoplasticity, and stability over a wide range of pH in the presence of a variety of salts. The viscosity of PS 3a35 was relatively insensitive to increasing temperature, whereas that of PS 3a24 showed an irreversible drop on heating.     

Comparison of Acetohydroxy-Acid Synthetases from Two Extreme Thermophilic Bacteria

The acetohydroxy-acid synthetases from two extreme bacterial thermophiles, Thermus aquaticus and Bacillus sp., have been studied. The two enzymes have different pH optima, 8 and 6, respectively, and both are feedback inhibited by valine. The inhibition is of interest because it is not expressed below 60 C, but only at higher temperatures which are optimal for catalytic activity. Valine inhibition in T. aquaticus was noncompetitive, whereas in Bacillus sp., it was competitive. Isoleucine (10(-3) M) also inhibited the two enzymes, whereas leucine (10(-3) M) did not. There was no concerted feedback when the amino acids were added in together. The sensitivity of the enzymes to valine could not be removed by HgCl(2). Both enzymes required Mg(2+) and thiamine pyrophosphate for optimal activity, whereas only the enzyme from T. aquaticus required flavine adenine dinucleotide in addition. None of these cofactors was essential for the feedback inhibition caused by valine. The enzymes from both bacteria could be repressed, but only in the presence of all three branched-chain amino acids indicating that, as in Escherichia coli and Salmonella typhimurium, the repression system is multivalent.     

小麦,玉米接种耐氨固氮菌试验初步分析

１９８９—１９９２年,在广东省部分县市进行了小麦、王米施用耐氨固氮菌大田对比试验,小麦接种耐氨固氮菌后,接菌区小麦的穗氏、有效穗、每穗粒数均比不接菌区明显增加,株高、成穗率、千粒重比对照略有增加,平均每亩比对照增产１６．７ｋｇ干麦,平均增产率为８．１％。玉米接种耐氨固氮菌后,接菌区玉米的茎粗、收获时的青叶片数、单苞重均比对照区明显增加,秃顶度比对照区明显减小,晒干率：出米率略有增加,平均每亩比对照增产５２．８ｋｇ玉米,平均增产率为１１．８９％。     

Two Related Rolling Circle Replication Plasmids from Salt-Tolerant Bacteria

In a range of salt-tolerant bacteria isolated from soil, rhizosphere, and phyloplane, cross-hybridization tests revealed a group of seven plasmids which were chosen for further study. Two plasmids (pSH1418 and pSH1451) were picked as representative examples of the two related subgroups. Restriction mapping and Southern blotting identified a region common to the two plasmids which later was identified as encoding the replication functions. We were unable to join these plasmids to high-copy-number vectors but this was possible with low-copy-number IncP vectors. InEscherichia coli,cloned plasmids pSH1418 and pSH1451 conferred salt tolerance but the phenotype was unstable, with the loss of salt tolerance apparently being correlated with structural instability of the plasmid DNA. Plasmid pSH1451 was sequenced and shown to be closely related to RCR plasmids of Gram-positive bacteria. The host of this plasmid was classified asBacillus pumilusby rDNA typing and lipid profiling by gas chromatography. A number of open reading frames (orfs) which could code for salt tolerance or other functions were identified in the plasmid sequence. Sequence similarity to previously sequenced genes suggested that the products of orf4 and orf5 may work together to transport a molecule such as aspartate ion that may promote osmotolerance.     

Two Novel Bacteriophages of Thermophilic Bacteria Isolated from Deep-Sea Hydrothermal Fields

Bacteriophages of thermophiles are of great interest due to their important roles in many biogeochemical and ecological processes. However, no virion has been isolated from deep-sea thermophilic bacteria to date. In this investigation, two lytic bacteriophages (termed Bacillus virus W1 and Geobacillus virus E1) of thermophilic bacteria were purified from deep-sea hydrothermal fields in the Pacific for the first time. Bacillus virus W1 (BVW1) obtained from Bacillus sp. w13, had a long tail (300nm in length and 15 nm in width) and a hexagonal head (70 nm in diameter). Another virus, Geobacillus virus E1 (GVE1) from Geobacillus sp. E26323, was a typical Siphoviridae phage with a hexagonal head (130 nm in diameter) and a tail (180 nm in length and 30 nm in width). The two phages contained double-stranded genomic DNAs. The genomic DNA sizes of BVW1 and GVE1 were estimated to be about 18 and 41 kb, respectively. Based on SDS-PAGE of purified virions, six major proteins were revealed for each of the two phages. The findings in our study will be very helpful to realize the effect of virus on thermophiles as well as the communities in deep-sea hydrothermal fields.     

Nitrogen-fixing activity in peat soils from a raised bog

The nitrogenase (acetylene reductase) activity in monolithic and minced peat samples was found to be low, no more than 0.014-0.022 mg N/(kg h). Incorporation of the 15N2 isotope into organic compounds of peat soil was from 2.71-8.13 mg N/kg over 15 days. The nitrogen-fixing activity was the highest in a 10-20 cm layer of soil and much lower in the upper (under green moss) and deeper (20-30 cm) layers. The addition of glucose to soil samples stimulated nitrogen fixation considerably after 18-26 h. The maximum nitrogenase activity (3.5-3.8 mg N/(kg h)) observed after 60-70 h coincided with the peak of respiratory activity. A repeated addition of glucose after its exhaustion increased nitrogenase activity without a lag period to 8.5 mg N/(kg h). Investigation of the effect of environmental factors (temperature, pH, aeration, and light intensity) on potential nitrogen-fixing activity in peat samples revealed that nitrogen fixation could proceed in a wide range of pH values (from 3.0 to 7.5) and temperatures (from 5 to 35 degrees C). The nitrogen-fixing bacteria belonging to different trophic groups were enumerated by using nitrogen-free media with pH values and mineralization levels close to those in situ. In samples of peat soil, diazotrophic methanol-utilizing bacteria prevailed (2.0-2.5 x 10(6) cells/g); the second largest group was facultatively anaerobic bacteria of the family Enterobacteriaceae.     

Assessing Riparian Quality Using Two Complementary Sets of Bioindicators

Biological indicators are being increasingly used to rapidly monitor changing river quality. Among these bioindicators are macroinvertebrates. A short-coming of macroinvertebrate rapid assessments is that they use higher taxa, and therefore lack taxonomic resolution and species-specific responses. One subset of invertebrate taxa is the Odonata, which as adults, are sensitive indicators of both riparian and river conditions. Yet adult Odonata are not necessarily an umbrella taxon for all other taxa. Therefore, we investigated whether the two metrics of aquatic macroinvertebrate higher taxa and adult odonate species might complement each other, and whether together they provide better clarity on river health and integrity than one subset alone. Results indicated that both metrics provide a similar portrait of large-scale, overall river conditions. At the smaller spatial scale of parts of rivers, Odonata were highly sensitive to riparian vegetation, and much more so than macroinvertebrate higher taxa. Odonate species were more sensitive to vegetation structure than they were to vegetation composition. Landscape context is also important, with the odonate assemblages at point localities being affected by the neighbouring dominant habitat type. Overall, benthic macroinvertebrates and adult Odonata species provide a highly complementary pair of metrics which together provide large spatial scale (river system) and small spatial scale (point localities) information on the impact of stressors such as riparian invasive alien trees. As adult Odonata are easy to sample and are sensitive to disturbance at both small and large spatial scales, they are valuable indicators for rapid assessment of river condition and riparian quality.     

Hydrolysis of Selected Organophosphorus Insecticides by Two Bacteria Isolated from Flooded Soil

Flavobacterium sp. ATCC 27551 hydrolysed both diethyl (parathion and diazinon) and dimethyl (methyl parathion and fenitrothion) phosphorothioates while Pseudomonas sp. ATCC 29353 hydrolysed only diethyl (parathion and diazinon) phosphorothioates. Glucose inhibited the hydrolysis of parathion by Pseudomonas sp., but not by Flavobacterium sp. Evidently, the Flavobacterium hydrolase differs from that of Pseudomonas sp. The Pseudomonas sp. converted 4-nitrophenol to 4-aminophenol in the presence of glucose and to nitrite in its absence; 4-nitrophenol was not metabolized by the Flavobacterium sp.     

Synergism of Glycoside Hydrolase Secretomes from Two Thermophilic Bacteria Cocultivated on Lignocellulose

Two cellulolytic thermophilic bacterial strains, CS-3-2 and CS-4-4, were isolated from decayed cornstalk by the addition of growth-supporting factors to the medium. According to 16S rRNA gene-sequencing results, these strains belonged to the genus Clostridium and showed 98.87% and 98.86% identity with Clostridium stercorarium subsp. leptospartum ATCC 35414^T and Clostridium cellulosi AS 1.1777^T, respectively. The endoglucanase and exoglucanase activities of strain CS-4-4 were approximately 3 to 5 times those of strain CS-3-2, whereas the β-glucosidase activity of strain CS-3-2 was 18 times higher than that of strain CS-4-4. The xylanase activity of strain CS-3-2 was 9 times that of strain CS-4-4, whereas the β-xylosidase activity of strain CS-4-4 was 27 times that of strain CS-3-2. The enzyme activities in spent cultures following cocultivation of the two strains with cornstalk as the substrate were much greater than those in pure cultures or an artificial mixture of samples, indicating synergism of glycoside hydrolase secretomes between the two strains. Quantitative measurement of the two strains in the cocultivation system indicated that strain CS-3-2 grew robustly during the initial stages, whereas strain CS-4-4 dominated the system in the late-exponential phase. Liquid chromatography-tandem mass spectrometry analysis of protein bands appearing in the native zymograms showed that ORF3880 and ORF3883 from strain CS-4-4 played key roles in the lignocellulose degradation process. Both these open reading frames (ORFs) exhibited endoglucanase and xylanase activities, but ORF3880 showed tighter adhesion to insoluble substrates at 4, 25, and 60°C owing to its five carbohydrate-binding modules (CBMs).     

M BAND PROTEIN : Two Components Isolated from Chicken Breast Muscle

M band protein can be specifically extracted from fresh chicken breast muscle myofibrils suspended in 5 mM Tris-HCl pH 8.0. During discontinuous polyacrylamide gel electrophoresis the isolated protein separates into three bands which can be identified as two separate components (A, B) and a complex of the two. When partially purified fractions of the separated components are combined, an increase in the intensity of the band containing the complex can be shown. The polypeptide chain weights of the two components are 100,000 (A) and 40,000 (B) daltons as estimated by sodium dodecyl sulfate- (SDS-) polyacrylamide gel electrophoresis. Antibody prepared against total M band protein stains only the M band of the myofibril and is completely absorbed by M band protein. M band protein also absorbs the M band staining specifically from antibody which stains both I and M bands. Immunodiffusion data indicate that anti-M band is a mixture of two specific antibodies, one against each component.     

云南两种地衣茶:白雪茶(Thamnolia spp.)和红雪茶(Lethariella spp.)的营养成分分析

“红雪茶”和“白雪茶”是滇西北少数民族传统饮用的地衣保健茶;其中,“红雪茶”混杂了梅衣科(Parmeliaceae)金丝属(Lethariella)中的4个地衣种:金丝绣球(Lethariellacashmeriana),金丝刷(L.cladonioides),柔金丝(L.sernanderi)和金丝带(L.zahlbruckneria);“白雪茶”包含了雪茶属(Thamnolia)中的两个种,即:雪茶和雪地茶(Thamnoliavermicularis&T.subuliforms)。利用常规方法测定了两种地衣茶的主要营养成分,并与常见饮茶进行比较,测定结果显示:红雪茶和白雪茶含有多种营养成分,红雪茶粗蛋白质含量为2.69g/100g·DW,粗脂肪3.42g/100g·DW,总糖、可溶性糖、灰分含量分别为5.04g/100g、0.35g/100g、1.74g/100g·DW;白雪茶的粗蛋白质含量为2.81g/100g·DW,粗脂肪2.91g/100g·DW,总糖、可溶性糖、灰分含量分别为0.99g/100g、0.27g/100g、4.18g/100g·DW;两种地衣茶均含有17种氨基酸和多种矿物元素,具有一定营养价值;而两种地衣营养成分的含量存在差异。     

Culturable Bacteria in Subglacial Sediments and Ice from Two Southern Hemisphere Glaciers

Viable prokaryotes have been detected in basal sediments beneath the few Northern Hemisphere glaciers that have been sampled for microbial communities. However, parallel studies have not previously been conducted in the Southern Hemisphere, and subglacial environments in general are a new and underexplored niche for microbes. Unfrozen subglacial sediments and overlying glacier ice samples collected aseptically from the Fox Glacier and Franz Josef Glacier in the Southern Alps of New Zealand now have been shown to harbor viable microbial populations. Total direct counts of 2–7 × 10⁶ cells g^–1 dry weight sediment were observed, whereas culturable aerobic heterotrophs ranged from 6–9 × 10⁵ colony-forming units g^–1 dry weight. Viable counts in the glacier ice typically were 3–4 orders of magnitude smaller than in sediment. Nitrate-reducing and ferric iron–reducing bacteria were detected in sediment samples from both glaciers, but were few or below detection limits in the ice samples. Nitrogen-fixing bacteria were detected only in the Fox Glacier sediment. Restriction fragment analysis of 16S rDNA amplified from 37 pure cultures of aerobic heterotrophs capable of growth at 4°C yielded 23 distinct groups, of which 11 were identified as -Proteobacteria. 16S rDNA sequences from representatives of these 11 groups were analyzed phylogenetically and shown to cluster with bacteria such as Polaromonas vacuolata and Rhodoferax antarcticus, or with clones obtained from permanently cold environments. Chemical analysis of sediment and ice samples revealed a dilute environment for microbial life. Nevertheless, both the sediment samples and one ice sample demonstrated substantial aerobic mineralization of ¹⁴C-acetate at 8°C, indicating that sufficient nutrients and viable psychrotolerant microbes were present to support metabolism. Unfrozen subglacial sediments may represent a significant global reservoir of biological activity with the potential to influence glacier meltwater chemistry.     

Nitrogen-fixing azotobacters from mangrove habitat and their utility as marine biofertilizers

A dearth of information is available for nitrogen-fixing bacteria in coastal mangroves, and hence, the present study has been undertaken to analyse 44 root and associated soil samples, derived from a mangrove habitat of southeast coast of India. The root samples exhibit high counts of total heterotrophic bacteria and azotobacters along with high rates of nitrogen fixation, as compared to the rhizosphere soil samples. Among the plant species, Bruguiera cylindrica records high microbial counts and nitrogen fixation. From the samples analysed, three species of Azotobacter, viz., A. chroococcum, A. virelandii and A. beijerinckii were isolated, purified and identified. These species exhibit high growth, nitrogen fixation and in vitro production of phytohormone (Indole Acetic Acid, IAA) at NaCl salinity of 30 g l⁻¹. The azotobacters, which were inoculated with Rhizophora seedlings, increased significantly the average root biomass up to by 98.2%, the root length by 48.45%, the leaf area by 277.86%, the shoot biomass by 29.49% as compared to controls and they also increased the levels of total chlorophylls and carotenoids up to by 151.0% and 158.73%, respectively. Thus, azotobacterisation is beneficial in raising vigorous seedlings of mangroves in coastal wetlands.     

Amino Acid Composition and Terminal Sequences of Ferredoxins from Two Photosynthetic Green Bacteria

The amino acid composition of ferredoxins from Chlorobium thiosulfatophilum 8327 and Chloropseudomonas ethylicum, like C. thiosulfatophilum Tassajara, resembled ferredoxins from nonphotosynthetic anaerobes rather than Chromatium; the terminal sequences, however, more closely resembled Chromatium ferredoxin.     

Role of Two Chloride-Binding Sites in Functioning of Testicular Angiotensin-Converting Enzyme

Modeling the structure of the C-domain of bovine angiotensin-converting enzyme revealed two putative chloride-binding sites. The kinetic parameters, K(m) and k(cat), of hydrolysis of the substrate Cbz-Phe-His-Leu catalyzed by the testicular (C-domain) enzyme were determined over a wide range of chloride concentrations. Chloride anions were found to be enzyme activators at relatively low concentrations, but they inhibit enzymatic activity at high concentrations. A general scheme for the effect of chloride anions on activity of the C-domain of bovine angiotensin-converting enzyme accounting for binding the "activating" and "inhibiting" anions is suggested.