Effect of pesticides on hydrogen metabolism of Rhodobacter sphaeroides and Rhodopseudomonas palustris

Abstract: The present study reports the effect of 2,4- d , quinalphos, monocrotophos, captan and carbendazim on the hydrogen metabolism (nitrogenase, photoproduction of hydrogen and hydrogenase activities) of two purple non-sulfur bacteria isolated from paddy soils. In general, the pesticides were found to be inhibitory to both nitrogenase and hydrogen photoproduction activities of both the organisms, and their effect on hydrogenase-mediated reactions varied with the pesticides used and the organisms.     

Evidence of covalent modification of glutamine synthetase in the purple sulfur bacterium Thiocapsa roseopersicina

Abstract It was shown that glutamine synthetase of purple sulfur bacterium Thiocapsa roseopersicina is regulated by covalent modification. This conclusion is made on the basis of results showing that: (i) incubation of cells under conditions of nitrogen deprivation in the light lead to an increase of glutamine synthetase activity; (ii) addition of ammonium to nitrogen-starved cell suspensions caused a rapid decrease of glutamine synthetase activity; (iii) inhibition of glutamine synthetase by feedback modifiers was higher in ammonium-treated cells than in those starved for a nitrogen source; (iv) treatment of purified glutamine synthetase and cell-free extracts with phosphodiesterase was accompanied by an increase of glutamine synthetase activity, indicating the cleavage of modifying residues covalently bound to glutamine synthetase molecules.     

A new species of the ghost shrimp genus Neocallichirus Sakai, 1988 (Decapoda: Axiidea: Callianassidae) from the southwestern Atlantic

ABSTRACT

A new species of ghost shrimp, Neocallichirus pinheiroi, is described based on specimens collected in subtidal habitats of Saquaira beach, northeastern coast of Brazil. This new species resembles N. lemaitrei Manning, 1993, but differs from it primarily in having a third maxilliped propodus expanded ventrally, and in the case of males, a large subtriangular tooth on the cutting edge of the major cheliped dactylus. Diagnostic features of the new species include: (i) frontal margin of carapace with rounded lateral projections not exceeding rostrum distal margin, (ii) third maxilliped carpus with row of sclerotized setae on median internal surface, (iii) minor cheliped with cutting edge of dactylus microscopically pectinate, (iv) endopod of male second pleopod with appendices interna and masculina. This is the seventh described species of the genus Neocallichirus from the western Atlantic and the fourth report of this genus in Brazil. A key for identification of western Atlantic species belonging to the genus is provided.     

Endosymbiotic purple non-sulphur bacteria in an anaerobic ciliated protozoon

Abstract The marine ciliate Strombidium purpureum Kahl harbours endosymbiotic purple non-sulphur bacteria. The bacteria contain bacteriochlorophyll a and the carotenoid spirilloxanthin, and they have photosynthetic membranes and cell walls. The ciliates require light for survival and growth under anaerobic conditions; in the dark the cells prefer microaerobic conditions. The ciliates show a photosensory behaviour, and they accumulate in light at wave lenghts corresponding to the absorption spectrum of the symbionts. The findings are discussed in terms of theories on the endosymbiotic origin of mitochondria.     

Localization of hydrogenase in the purple sulphur bacterium Thiocapsa roseopersicina

The localization of hydrogenase in the phototrophic bacterium Thiocapsa roseopersicina was investigated by subcellular fractionations, and transmission electron microscopic immunocytochemistry. By using sonicated cells and measuring in vitro hydrogenase activities in soluble and membrane fractions, respectively, a weak hydrophobic interaction between the hydrogenase enzyme and the T. roseopersicina membranes was observed. Polyclonal antisera directed against the purified hydrogenase were raised in rabbits and exhibited one band in native-PAGE/Western immunoblot analysis. Native-PAGE/activity stain confirmed the identity of this band as being hydrogenase. Immunocytolocalization experiments using ultrathin sections showed an internal localization of the hydrogenase enzyme. A higher specific labeling was associated with chromatophores, indicating a possible coupling of hydrogenase with the photosynthetic membranes in the T. roseopersicina cells.     

Laminated microbial ecosystems on sheltered beaches in Scapa Flow, Orkney Islands

Abstract Laminated microbial sediment ecosystems which develop in the upper tidal zone of Scapa Flow beaches, Orkney Islands were investigated with respect to depth profiles of chlorophyll a , bacteriochlorophyll a , pH, redox, oxygen and the following inorganic sulfur compounds: free sulfide, FeS, polysulfides, polythionates, elemental sulfur and thiosulfate. In addition, particle size distribution and light penetration were determined at all sampling locations.
Three main types of laminated sediment ecosystems were recognized, designated the 'classical' type (layer of cyanobacteria underlain by layer of purple sulfur bacteria), the 'single-layer' type (chlorophyll a containing organisms absent, purple sulfur bacteria at sediment surface), and the 'inverted' type (chlorophyll a containing organisms underlying purple sulfur bacteria). The dominant purple sulfur bacterium was Thiocapsa roseopersicina and Chromatium vinosum was observed less commonly. The principal cyanobacterium found in these sulfureta was Oscillatoria sp.
The depth horizon at which maximum populations of purple sulfur bacteria were recorded often did not coincide with the sulfide/oxygen interface but was located closer to the sediment surface where polysulfides, polythionates, elemental sulfur and occasionally thiosulfate were present. The structure of these sulfureta is discussed in relation to the chemolithotrophic growth capacities of Thiocapsa in the presence of oxygen.     

产紫色素真菌H-1的鉴定及其色素的理化性质和生物活性

从腐殖土样中分离得到一株产水溶性紫色素真菌,编号为H-1。通过对该真菌β-微管蛋白基因序列分析,并构建系统进化树进行初步鉴定,对色素性质如色素特征性吸收峰、溶解性、稳定性、细胞增殖抑制活性、抗菌活性等进行研究。结果表明,H-1与萨氏曲霉(Aspergillus sydowii)的同源性达到了100%,属于萨氏曲霉。该色素在520 nm处有特征性吸收峰,极易溶于水,低浓度乙醇和甲醇溶液,不溶于其他非极性溶剂。该色素对光的稳定性表现为:紫外光>黑暗>-白光;100℃处理色素4 h,色素残存率为86.8%,热稳定性较好,在碱性条件下稳定,在Na+溶液残存率为99.9%,基本无损失。与正常人肝细胞HL-7702相比,该色素具有抑制人肝癌细胞HepG2增殖作用,其半数抑制浓度(IC50)为1.282 mg/mL;同时该色素具有清除羟自由基与超氧阴离子自由基的作用,也能明显抑制藤黄八叠球菌、金黄色葡萄球菌的生长,其最低抑菌浓度(minimal inhibitory concentration, MIC)均为195.312μg/mL,对大肠杆菌无明显抑菌活性。     

Enrichment of purple photosynthetic bacteria from earthworms

Abstract Numerous bacteria present in soil during its passage through the alimentary canal of earthworms resist digestive action and the antimicrobial defenses of the worms. Thus, several kinds of non-sulfur purple photosynthetic bacteria (Rhodospirillaceae) can be enriched from 'purees' of washed earthworms (or from intestinal contents of the worms) using a procedure that exploits the capacity to fix N₂ during anaerobic phototrophic growth with organic acid carbon sources. It appears that earthworm enrichments can be designed to provide highly selective methods for isolation of Rhodomicrobium vannielli and Rhodopseudomonas palustris , and perhaps of other purple bacteria. The extensive burrowing activities of earthworms undoubtedly contributes to the widespread dissemination of Rhodospirillaceae in soils.     

Community Structure of Macrobenthic Invertebrates in Sandy Beaches of the Jordan Gulf of Aqaba,Red Sea

Six sandy beach stations along the Jordan Gulf of Aqaba were selected for macrofaunal examination during November 1980. Fifteen core samples (0.01 m² to a depth of 10–15 cm) were taken at each station; five at the high tide line, five at the low tide line, and five midway. Twenty-two taxa were encountered from all stations. Polychaetes were the most diverse group with seven taxa, followed by molluscs and crustaceans with six and five taxa respectively. Animal diversity, using the Shannon-Wiener Index, was generally low. Based on the biological index value of McCLOSKEY (1970), seven taxa were considered the community dominants. These are: the polychaetes, Glycera tesselata, Pisione remota, Saccocirrus sp., and Perinereis nuntia; the isopod Eurydice arabica; a nemertean and an oligochaete.