Isolation and Some Properties of Alkalophilic Bacteria Utilizing Rayon Waste

Bacillus No. C-11 which utilized rayon waste was isolated. This strain belongs to the genus Bacillus from its morphological and biochemical characteristics but grew better in alkaline media than in neutral media. Residual sugars of rayon waste were 34.7 % after 2 days cultivation, 25.5% after 4 days and 7.0% after 9 days. Yeast extract and N-source, such as polypeptone or urea stimulated the utilization of rayon waste. The long period cultivation optimum pH was about 11, and the short period cultivation optimum pH was about 9. Partially purified hemicellulase from Bacillus No. C-11 was most active at pH 7, but still active at pH 10. The stable pH for this enzyme action was in the range of 5.5 to 9, and from the hemicellulose enzymatic digest, xylose, xylobiose, xylotriose and oligosaccharides were detected.     

Geomicrobiology of Cave Ferromanganese Deposits: A Field and Laboratory Investigation

Abstract

Unusual ferromanganese deposits are found in several caves in New Mexico. The deposits are enriched in iron and manganese by as much as three orders of magnitude over the bedrock, differing significantly in mineralogy and chemistry from bedrock-derived insoluble residue. The deposits contain metabolically active microbial communities. Enrichment cultures inoculated from the ferromanganese deposits produced manganese oxides that were initially amorphous but developed into crystalline minerals over an 8-month period and beyond; no such progression occurred in killed controls. Phylogenetic analyses of sequences from clone libraries constructed from culture DNA identified two genera known to oxidize manganese, but most clones represent previously unknown manganese oxidizers. We suggest that this community is breaking down the bedrock and accumulating iron and manganese oxides in an oligotrophic environment.     

霉菌对军用枪支的侵蚀与防治

为了有效保存军用枪支,防止霉菌的侵蚀危害,用人工接种培养方法,将军标指示菌接种到枪支上。第1组置于加防霉剂和干燥剂密封袋中,第2组置于不加防霉剂和干燥剂敞口袋中。在温度(30±1)℃,湿度(95±5)%交替变化的条件下对军用枪支连续进行试验。结果表明,第1组样品长霉极少,危害小,长霉面积仅为0.103%~0.304%。而第2组样品长霉面积大,危害严重,长霉面积为11.37%~22.94%,是第1组的110.4~133.4倍。因此,选择适合的防霉剂和干燥剂在密封条件下,有利于抑制霉菌生长,是防止霉菌对军用枪支危害的有效方法。     

Instrumental analysis of microbiologically influenced corrosion

Appropriate application of techniques for detection andmonitoring of microbiologically influenced corrosion isessential for understanding the mechanistic nature of theinteractions and for obtaining control methods. This paperreviews techniques and methods applied tomicrobiologically influenced corrosion in recent years.The techniques presented in this paper includeelectrochemical noise measurement, concentric electrodes,scanning vibrating electrode mapping, electrochemicalimpedance spectroscopy, atomic force microscopy,confocal laser microscopy, Fourier transform infraredspectroscopy, x-ray photoelectron spectroscopy, Augerelectron spectroscopy, extended x-ray absorption finestructure and utilization of piezoelectric materials. Thesetechniques are reviewed regarding the heterogeneouscharacteristics of microbial consortia and their possibleinfluences on metal substrata. We hope this review willmotivate application and combination of new techniquesfor practical detection and on-line monitoring of theimpact of biofilms on engineering alloys.     

The influence of sunlight on the localized corrosion of UNS S31600 in natural seawater

Tests were conducted on the performance of UNS S31600 stainless steel (SS) in a natural day/night cycle vs full darkness under conditions of natural marine biofilm accumulation. In quiescent flowing seawater tests in the laboratory as well as under natural immersion in the sea, diffuse sunlight (～10% of natural) counteracted the influence of marine biofilms and produced substantial inhibition of the corrosion of SS. Thus, the probabilities (percentage attack) and propagation rates (depths of attack) in multiple crevice tests were substantially lower in the day/night cycle than in the dark. A benefit was also observed for welded SS in terms of the time to corrosion initiation and the mass loss. SS in the passive state showed broader passive regions, well-defined breakdown potentials and markedly smaller anodic and cathodic current densities under the diurnal cycle. The overall reduction in corrosion is attributed to a combination of electrochemical photoinhibition and simultaneous photoinactivation of microbially mediated metal redox reactions linked to cathodic kinetics. These data offer fresh insights into the behaviour of SS under practical seawater situations and the proposed potential use of illumination in the mitigation of biologically influenced consequences.     

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor was investigated over a 10-month period in a hotel. Planktonic and sessile numbers of sulphate reducing bacteria (SRB) and heterotrophic bacteria were monitored. The corrosion rate was determined by the weight loss method. The corrosion products were analyzed by energy dispersive X-ray spectroscopy and X-ray diffraction. A mineralized, heterogeneous biofilm was observed on the coupons. Although a biocide and a corrosion inhibitor were regularly added to the cooling water, the results showed that microorganisms, such as SRB in the mixed species biofilm, caused corrosion of galvanized steel. It was observed that Zn layers on the test coupons were completely depleted after 3?months. The Fe concentrations in the biofilm showed significant correlations with the weight loss and carbohydrate concentration (respectively, p?<?0.01 and p?<?0.01).     

Cofactor Requirements of Tryptophanase from Proteus rettgeri

Crystalline tryptophanase prepared from the cells of Proteus rettgeri is inactive in the absence of added pyridoxal phosphate. Half-maximal enzyme activity is obtained at a concentration of 1.81 µm. Binding of pyridoxal phosphate to the apoenzyme is accompanied by pronounced increase in absorbance at 340 and 420 nm. Holotryptophanase requires K⁺ or for its maximal activity, but Na⁺ is inactive. No appreciable spectral change was observed on changing the ionic environments.

The amount of pyridoxal phosphate bound to the enzyme was determined by equilibrium dialysis and spectrophotometric titration to be 4 moles per mole of enzyme. Reduction of holoenzyme with sodium borohydride results in a shift of the absorption peak at 420 to 336 nm. ?-Pyridoxyllysine was isolated from the acid hydrolyzate of the reduced holoenzyme by paper chromatography and electrophoresis.

Addition of the substrate, l-tryptophan, or the competitive inhibitor, l-alanine, to the holoenzyme causes appearance of a new peak near 500 nm which disappears as the substrate is decomposed but remains unchanged in the presence of the inhibitor. The similar spectral change was observed by the addition of pyruvate, ammonia and indole to the holoenzyme.     

氯盐型融雪剂的环境影响及其替代材料研发进展

传统氯盐型融雪剂对环境的负面影响日益凸显,亟需研发价格低廉、环境影响较弱、融雪效果良好的环境友好型融雪替代材料。论文综述了现有氯盐型融雪剂应用现状,及其对土壤环境、水环境、植物和交通基础设施等的影响机理,并详细阐述了非氯型和混合型融雪剂替代材料的研发状况与应用成效。针对目前替代融雪材料开发和应用中所存在的问题,提出了环境友好融雪剂的研制发展方向以及减轻其环境危害行之有效的对策。     

Metallic dental material biocompatibility in osteoblastlike cells

Ions released from metallic dental materials used in orthodontic appliances could induce undesirable effects on cells and tissues. This study evaluates the biocompatibility of two of the most labile components of metallic dental alloys on osteoblastlike cells. The influence of protein and ions on metal dissolution properties is also investigated using different electrolyte solutions. Morphological alterations, cell growth, and differentiation of osteoblasts were assessed after exposure to pure metals (Ag, Cu, Pd, Au) and Ni−Ti alloy and correlated with the kinetics of elements released into the culture media. Results showed that Cu and Ag were the most cytotoxic elements and the other metals were biocompatible with the osteoblasts. The parameters of biocompatibility were correlated with the levels of ions detected into the culture media. Metal ions induced cell death through early mitosis arrest, apoptotic phenomena, and necrotic processes. Voltammograms showed that anions and proteins interfered in the corrosion process. Fetal bovine serum (FBS) strongly affected the electrochemical process, decreasing the oxidation rate of the metals. In conclusion, copper and silver ions showed a time-dependent low biocompatibility, which correlated with the concentration of released ions. The dissolution of the metallic materials was dependent on the composition of the simulated biological media.