Allergenicity of airborne cyanobacteria Phormidium fragile and Nostoc muscorum

In recent times, airborne microorganisms and their constituents have become prominent safety and health concern. Ongoing climatic changes coupled with unwarranted human activities have significantly deteriorated the ambient air quality. In certain environments, airborne algae contribute significantly to the total biological load of the atmosphere, hitherto dominated by bacteria and fungi. Present study was aimed to investigate the allergenic potency of two frequent viable algal forms i.e., Phormidium fragile and Nostoc muscorum found in the atmosphere of Varanasi City, India. To test the allergenic potency, crude extracts of these strains were subjected to intra-dermal allergy test and subsequent leukocyte counts, which revealed their allergenic nature. Both the species varied in their allergenic potency. N. muscorum appeared to be more allergenic than P. fragile. However, when the allergens were mixed in equal amounts, the severity of allergenicity increased significantly. A limited pattern of cross-reactivity between the species was also evident.     

Toxicity of carbofuran to blue-green alga Nostoc muscorum.

Effect of commercial grade pesticide furadan (3% a.i. as carbofuran) was studied on the survival, growth and nitrogen fixation of blue-green alga Nostoc muscorum. The lower concentration of furadan i.e. 25 microgram/ml enhanced survival, growth and nitrogen fixation in the alga whereas these were gradually inhibited in higher concentrations (50--1000 microgram/ml) and the presence of more than 1200 microgram/ml was algicidal. The preliminary observations revelaed that pesticide is biodegraded by the alga.     

Effect of three nitrophenols on carbon metabolism in Nostoc muscorum and Chlorella vulgaris

Carbon metabolism in selected strains of Nostoc muscorum and Chlorella vulgaris grown in the presence of three nitrophenols [o-nitrophenol, m-nitrophenol and 2,4-dinitrophenol] was assessed by examining activities of the enzymes such as amylase, starch phosphorylase, fructose 1,6-biphosphatase, sucrose phosphate synthase, and invertase. Marked alterations were observed in activities of the enzymes involved in starch metabolism. The cellular content of starch in nitrophenol-grown cultures was significantly reduced, whereas the levels of nonreducing and reducing sugars significantly increased. There was a significant increase in the activities of amylase and phosphorylase, and these alterations are probably responsible for the decreased amount of starch in the cultures. Furthermore, significant changes were noticed in activities of the enzymes involved in synthesis of sucrose as well.     

Impact of nitrophenols on the photosynthetic electron transport chain and ATP content in Nostoc muscorum and Chlorella vulgaris

Concentration-dependent inhibition of the photosynthetic electron transport chain (photosystem I (PS I), photosystem II (PS II) and whole chain reaction) and ATP content was observed in Nostoc muscorum and Chlorella vulgaris grown with o-nitrophenol, m-nitrophenol, or 2,4-dinitrophenol. Although the extents of inhibition of the photosynthetic electron transport chain in both organisms were similar, PS II was more sensitive than PS I and whole chain reaction to the nitrophenols. Depletion of the ATP pool was noted in nitrophenol-grown cultures, probably as a consequence of nearly complete inhibition of the photosynthetic electron transport chain.     

Effects of three pesticides on MSX-induced ammonia photoproduction by the cyanobacterium Nostoc linckia

Three pesticides (2,4-D, basalin, aldrin) inhibited L-methionine-DL-sulfoximine (MSX)-induced photoproduction of ammonia by the nitrogen-fixing cyanobacterium Nostoc linckia. Combinations of pesticides and MSX were inhibitory except at low concentrations (100 and 500 micrograms/ml) of 2,4-D which stimulated NH+4 production. Similar results were obtained when pesticides were added 6 hr after the addition of MSX, but the inhibition was weaker. When MSX was added to the culture 6 hr after the addition of pesticides, the pesticides stimulated NH+4 photoproduction. Similar results were obtained on nitrogenase activity of the organism.     

Differential physiological and biochemical responses of two cyanobacteria Nostoc muscorum and Phormidium foveolarum against oxyfluorfen and UV-B radiation

In the present study, degree of tolerance and tolerance strategies of two paddy field cyanobacteria viz. Nostoc muscorum and Phormidium foveolarum against oxyfluorfen (10 and 20 μg ml⁻¹) and UV-B (7.2 kJ m⁻² d⁻¹) stress were investigated. Oxyfluorfen and UV-B decreased growth, photosynthesis, nutrient uptake, nitrate reductase, acid and alkaline phosphatase activities, which accompanied with the increase in the level of oxidative stress. However, growth was more affected in N. muscorum than P. foveolarum. Antioxidants exhibited differential responses against oxyfluorfen and UV-B stress. Ascorbate and proline levels were higher in P. foveolarum. A protein of 66 kDa was expressed in N. muscorum, however, it was absent in P. foveolarum than those of N. muscorum. Besides this, a protein of 29 kDa appeared in P. foveolarum under all the treatments, but it was present only in control cells of N. muscorum cells. Overall results indicated resistant nature of P. foveolarum against oxyfluorfen and UV-B stress in comparison to N. muscorum.     

Toxicity of nickel and silver to Nostoc muscorum: interaction with ascorbic acid, glutathione, and sulfur-containing amino acids

Exposure of Nostoc muscorum to different concentrations of Ni and Ag brought about reduction in growth, carbon fixation, heterocyst production, and nitrogenase activity and increase in the loss of ions (K+, Na+). In an attempt to ameliorate the toxicity of test metals by ascorbic acid, glutathione, and sulfur-containing amino acids (L-cysteine and L-methionine), it was found that the level of protection by ascorbic acid and glutathione was more for Ag than Ni. However, metal-induced inhibition of growth and carbon fixation was equally ameliorated by methionine. But the level of protection by cysteine was quite different, i.e., 27% for Ni and 22% for Ag. Protection of metal toxicity in N. muscorum by amino acids lends further support to self-detoxifying ability of cyanobacteria because they are known to synthesize all essential amino acids.     

Purification and characterization of corrinoid-compounds from the dried powder of an edible cyanobacterium, Nostoc commune (Ishikurage)

Vitamin B12 content (98.8 +/- 5.6 microg/100 g dry weight) of an edible cyanobacterium, Nostoc commune (Ishikurage) was determined by the Lactobacillus delbrueckii ATCC 7830 microbiological method. Bioautography with vitamin B12-dependent Escherichia coli 215 indicated that N. commune contained two (main and minor) corrinoid-compounds. These corrinoid-compounds were purified to homogeneity from the dried algal cells and characterized. The main and minor purified corrinoid-compounds were identified as pseudovitamin B12 and vitamin B12, respectively, on the basis of silica gel 60 TLC, C18 reversed-phase HPLC, 1H NMR spectroscopy, and UV-visible spectroscopy. These results suggest that the bacterial cells are not suitable for use as a vitamin B12 source, especially in vegetarians.     

The involvement of the antioxidant system in protection of desert cyanobacterium Nostoc sp. against UV-B radiation and the effects of exogenous antioxidants

In this study, we found that UV-B radiation decreased photosynthetic activity and boosted lipid peroxidation of desert Nostoc sp., and exogenous chemicals (ascorbate acid (ASC), N-acetylcysteine (NAC), and sodium nitroprusside (SNP)) had obvious protective effects on photosynthesis and membranes under UV-B radiation. High-concentration SNP boosted the activities of antioxidant enzymes, but low-concentration SNP reduced the activities of antioxidant enzymes. Both NAC and ASC treatments of cells decreased activities of antioxidant enzymes. The results suggested that those chemicals possibly had different mechanisms of protection of algae cells against UV-B radiation. SNP might play double roles as a signal molecule in the formation of algae cell protection of Photosystem II under UV-B radiation and as a (reactive oxygen species) scavenger, while NAC and ASC might function as antioxidant reagents or precursors of other antioxidant molecules, which could protect cells directly against ROS initiated by UV-B radiation.     

Effect of heavy metal stress on proline, malondialdehyde, and superoxide dismutase activity in the cyanobacterium Spirulina platensis-S5

This study investigated toxic impacts of lead, copper, and zinc over a concentration gradient of 0.05-0.20 mg/L on proline, malondialdehyde (MDA), and superoxide dismutase (SOD) in the cyanobacterium Spirulina platensis-S5. Despite a reduction in growth of the test microorganism, its MDA, SOD, and proline contents increased under the heavy metal stress, corresponding to the concentration of the metal ion in the culture medium. Increased amount of MDA was indicative of formation of free radicals in the test microorganism under heavy metals stress(es), while increased levels of SOD and proline pointed to the occurrence of a scavenging mechanism.     

Effect of bimetallic combinations of Ni, Cr, and Pb on growth, uptake of nitrate and ammonia, 14CO2 fixation, and nitrogenase activity of Nostoc muscorum

The toxicity of Cr, Ni, and Pb individually as well as in combination (Cr + Ni, Cr + Pb, Ni + Pb) on growth, final yield, uptake of NO3- and NH4+, photosynthesis, and nitrogenase activity of Nostoc muscorum has been studied. All test metals, when used individually, depicted toxicity against the above-mentioned processes of test cyanobacterium. However, their interactive effect was found to be mostly of antagonistic type. Antagonism was more prevalent in those combinations containing nickel. In an attempt to measure the toxic potential of Cr, Ni, and Pb with respect to time, photosynthetic carbon fixation was found to be the more sensitive parameter followed by N2ase, NH4+ uptake, and NO3- uptake. Contrary to this, NH4+ uptake followed by carbon fixation, nitrate uptake, and N2ase appeared to be a preferred hierarchy sequence for measuring the toxicity of Cr, Ni, and Pb individually without any consideration of time. The toxicity potentials of metal combinations are generally less significant than those of individual metals. N2ase seems to be a more critical process followed by NH4+ uptake, photosynthesis, and NO3- uptake in measuring metal combination effects with respect to time. However, if time is not given any consideration, NH4+ uptake remains the most sensitive process for measuring metal combination effects. These results suggest that exposure time and treatment types are very important factors in evaluation of heavy metal toxicity.     

多种抗菌药物对医院感染鲍氏不动杆菌的耐药性差异分析

目的 探讨医院感染临床标本中鲍氏不动杆菌(ABA)的分布特征及耐药率,对预防控制突发细菌感染起着重要的作用.方法 回顾性分析医院2010年11月-2011年10月从住院患者各类感染标本中分离出的ABA感染情况及其耐药性.结果 391株ABA的分布以痰标本为主,占72.9％,其次为血液,占27.0％,支气管肺泡灌洗液,占17.0％；分布以神经内科、综合ICU和呼吸内科为主,分别占32.2％、23.8％和13.0％；该菌对氨苄西林、哌拉西林、头孢吡肟、头孢噻肟、左氧氟沙星、磺胺甲噁唑/甲氧苄啶的耐药率均＞71.0％,而且多药耐药率较高,对亚胺培南和美罗培南的耐药率仅为2.8％和3.3％.结论 ABA是医院感染的重要条件致病菌,其对抗菌药物耐药率高,应合理使用抗菌药物,注重检测和预防控制感染的发生.