Characteristics and role of the exocellular polysaccharides produced by five cyanobacteria isolated from phototrophic biofilms growing on stone monuments

Three coccoid and two filamentous cyanobacterial strains were isolated from phototrophic biofilms exposed to intense solar radiation on lithic surfaces of the Parasurameswar Temple and Khandagiri caves, located in Orissa State, India. Based on to their morphological features, the three coccoid strains were assigned to the genera Gloeocapsosis and Gloeocapsa, while the two filamentous strains were assigned to the genera Leptolyngbya and Plectonema. Eleven to 12 neutral and acidic sugars were detected in the slime secreted by the five strains. The secretions showed a high affinity for bivalent metal cations, suggesting their ability to actively contribute to weakening the mineral substrata. The secretion of protective pigments in the polysaccharide layers, namely mycosporine amino acid-like substances (MAAs) and scytonemins, under exposure to UV radiation showed how the acclimation response contributes to the persistence of cyanobacteria on exposed lithoid surfaces in tropical areas.     

Cyanobacteria-containing biofilms from a Mayan monument in Palenque,Mexico

Surfaces of buildings at the archaeological site of Palenque, Mexico, are colonized by cyanobacteria that form biofilms, which in turn cause aesthetic and structural damage. The structural characterization and species composition of biofilms from the walls of one of these buildings, El Palacio, are reported. The distribution of photosynthetic microorganisms in the biofilms, their relationship with the colonized substratum, and the three-dimensional structure of the biofilms were studied by image analysis. The differences between local seasonal microenvironments at the Palenque site, the bioreceptivity of stone and the relationship between biofilms and their substrata are described. The implications for the development and permanence of species capable of withstanding temporal heterogeneity in and on El Palacio, mainly due to alternating wet and dry seasons, are discussed. Knowledge on how different biofilms contribute to biodegradation or bioprotection of the substratum can be used to develop maintenance and conservation protocols for cultural heritage.     

Ecological approach to the genesis of calcium oxalate patinas on stone monuments

Summary The genesis of calcium oxalate patinas on stone monuments gives rise to controversial opinions. One of the proposed hypotheses links this phenomenon to the past presence of lichens on the exposed surfaces of monuments. However, the growth of a biological species cannot occur if environmental conditions are not compatible with its autoecology. Analysis of variations of the environmental factors that can act as «limiting factors» shows that in most monuments, the various exposures are not always compatible with biological growth. The environmental factor that seems to be the most limiting is the amount of surface water that is frequently below the range of tolerance of even the most xerophylous species. In the case of Trajan's column in Rome, the distribution of oxalate layers shows an opposite trend with respect to what we would expect for lichen colonization. Presently other kinds of biological colonization cannot be excluded.     

Fungal physiology and the formation of calcium oxalate films on stone monuments

Summary Extensive, uniform, yellow-brown films are observed on many monuments. The origin of these films, composed predominantly of calcium oxalate, has been investigated by several authors. Oxalate film formation may be related, in some cases, to the activity of such microorganisms as fungi, which presumably form oxalic acid via the metabolic transformation of organic substances already present on the stone. The present work provides an overview of the physiological factors affecting oxalate synthesis by fungi and of oxalic acid in fungi metabolism.     

The ATP-bioluminescence method for a rapid evaluation of the microbial activity in the stone materials of monuments

The examination of the state of conservation of works of art in stone includes the assessment of the presence of microbiological agents on the surface of the decayed monuments. These microorganisms can accelerate, via their metabolic activity, the decay process of the stone surface. At present this assessment is made with the traditional techniques for the microbiological examination of the soil, provides results only after a delay of 30 days. A bioluminescent ATP assay should provide rapid quantitation of actively growing organisms on the surface of a stone monument, and the applicability of this technique was verified on some samples of sandstone (Pietraforte) collected from a historic building (the Strozzi Palace) in Florence. These samples were evaluated for the amount of the ATP and the total number of microorganisms. The results obtained suggest that the bioluminescent assay could be suitable for detecting and quantitating the presence of microorganisms in a sample of stone.     

Characteristics and role of the exocellular polysaccharides produced by five cyanobacteria isolated from phototrophic biofilms growing on stone monuments

Three coccoid and two filamentous cyanobacterial strains were isolated from phototrophic biofilms exposed to intense solar radiation on lithic surfaces of the Parasurameswar Temple and Khandagiri caves, located in Orissa State, India. Based on to their morphological features, the three coccoid strains were assigned to the genera Gloeocapsosis and Gloeocapsa, while the two filamentous strains were assigned to the genera Leptolyngbya and Plectonema. Eleven to 12 neutral and acidic sugars were detected in the slime secreted by the five strains. The secretions showed a high affinity for bivalent metal cations, suggesting their ability to actively contribute to weakening the mineral substrata. The secretion of protective pigments in the polysaccharide layers, namely mycosporine amino acid-like substances (MAAs) and scytonemins, under exposure to UV radiation showed how the acclimation response contributes to the persistence of cyanobacteria on exposed lithoid surfaces in tropical areas.     

Evaluation of the effect of some biocides against organisms isolated from historic monuments

On the surfaces of monuments and buildings, organic and inorganic pollutants accumulate, as well as various microbial communities which contribute to stone decay. In order to control these organisms, we have tested some chemical products with biocide and water-repellent properties. Some of these products were tested in an agar diffusion test and on limestone slabs. Efficacy of the products and the microbial inhibition were studied with scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM) techniques. This revised version was published online in June 2006 with corrections to the Cover Date.     

Environmental factors affectingin vitro nitrogenase activity of cyanobacteria isolated from rice-fields

The nitrogen-fixing capacity of four cyanobacterial strains was tested in relation to heterotrophic ability, tolerance to combined nitrogen and adaptive capacity to changes in light intensity and pH. Strains (Anabaena variabilis UAM 202;Calothrix marchica UAM 214;Nodularia spumigena UAM 204,Nostoc punctiforme UAM 205) were isolated from the rice-fields of Valencia (Spain).C. marchica, was the only strain able to grow and to fix dinitrogen under heterotrophic conditions, with fructose and glucose. Fructose was the best substrate supporting growth and dinitrogen fixation in mixotrophy (growth in the light under conditions where CO₂ and organic carbon are assimilated simultaneously), photoheterotrophy (growth in the light on an organic compound in the absence of net CO₂ fixation) and heterotrophy (growth on an organic compound in the dark). Ammonium repressed nitrogenase more than nitrate. Full repression was observed only at concentrations of combined nitrogen higher than those usually found in rice-fields. Carbohydrates had a protective effect on nitrogenase against ammonium inhibition inC. marchica. All four strains showed increased nitrogenase activity when the light intensity was increased during assays. Variations of pH normally occurring in rice fields led to no important changes in nitrogenase activity inC. marchica. This fact, together with its potential for heterotrophic growth and tolerance to combined nitrogen, make this the most suitable of the four strains for inoculation experiments in rice fields.     

Diversity of phototrophic components in biofilms from Piperno historical stoneworks

We investigated phototrophic microorganisms dwelling on stone walls made of Piperno, a volcanic rock frequently used as construction material in historical buildings in Naples, Italy. Biofilms from three historical buildings in the center of the city and from a natural Piperno quarry located in a suburban area were examined. Light and electron microscopy, and molecular biology techniques allowed the identification of 17 species belonging to Cyanobacteria, Rhodophyta, Bacillariophyta, and Chlorophyta. Cyanobacteria were the dominant components in all the biofilms. No significant differences in microbial composition were observed for biofilms collected in autumn and spring, with minor exceptions for the quarry samples, where environmental conditions were relatively more stable than in the city. Results are discussed in comparison with information on microbial communities dwelling on other kinds of substrata commonly used in historical buildings in the Neapolitan area.     

洱海蓝藻爆发的时空特征及影响因子

湖泊生态环境对区域气候变化和流域人类活动十分敏感。随着流域的持续开发,洱海作为云贵高原第二大淡水湖泊面临着严重的生态与环境问题,主要包括水质恶化和生态功能的衰退,其中蓝藻水华问题尤为突出。针对湖泊现代监测数据存在时间序列较短、连续监测记录缺乏、监测位点不完全一致等问题,应用沉积物记录开展色素等多指标分析和环境变化重建研究,并对洱海湖区南、中、北3个湖盆的沉积物记录进行对比分析,从而探讨洱海富营养化与蓝藻爆发的历史与变化特征,并识别藻类响应模式的空间异同。沉积物色素记录结果表明,洱海蓝藻生物量变化具有明显的时空差异性,呈现由南至北,先后增加、最后呈现蓝藻水华全湖性持续爆发的模式。进一步的简约模型方差分解结果表明气候变暖和营养盐富集是洱海蓝藻生物量变化的主要驱动因子,此外相对较浅的南部湖盆还受到水位波动、水动力减弱、水生植物演化的综合影响。因此,在气候变暖的背景下,控制水体营养盐输入、合理调控湖泊水位、提高水体透明度并恢复水生植物是控制洱海蓝藻水华爆发和进行生态恢复的重要措施。     

蓝细菌固碳合成乳酸技术的发展与展望

乳酸是一种重要的工业化学品,被广泛应用于各个行业。近年来,随着聚乳酸(PLA)市场的兴起,乳酸原料的需求也在不断增加。糖基异养生产乳酸所带来的高昂成本与市场需求的矛盾吸引着研究人员积极寻找其他有利的解决方案。蓝细菌光合固碳生产乳酸是一种潜力巨大的新型原料供应策略,基于光合自养的细胞工厂,可以在单一平台上以太阳能为驱动力,从二氧化碳中直接生产出高光学纯度的乳酸。该方法原料廉价易得、过程简单可控、产物明确且易分离,同时达到节能减排和高附加值产品生产的双重效果,具有重要的研究与应用价值。文中回顾了蓝细菌固碳产乳酸技术的发展历程,从代谢基础、代谢工程策略、代谢动力学分析与技术应用等方面,梳理其研究进展和所遇到的技术难点,并对该技术的未来进行展望。     

Identification and study of growth and nitrogenase activity of nitrogen fixing cyanobacteria from tropical soil

Identification of cyanobacteria species has been performed on samples coming from two different harvest areas. The most important fixing belongs to Scytonema genus. The other genus identified are Nostoc and Lyngbia. Moreover, these cells are living closely with non-fixing cyanobacteria as well as with bacteria. The growth of cells as well as nitrogenase activity has been studied on a semi-axenic strain of Scytonema, a nitrogen fixing cyanobacterium, isolated from soil crusts. The cell growth is relatively show in liquid medium depleted in combined nitrogen. The growth rate increases when nitrates are supplied to cells. A release of ammonium is observed in medium during cell culture. This release exhibits several maxima and minima during cell growth. The heterocyst cells disappear within four days when filaments are growing in nitrates supplied medium. On the contrary, the heterocyst frequency increases up to more 5% in a nitrogen depleted medium. The heterocyst frequency reaches a maxima after 4 days of culture, then decreases later on. Nitrogenase activity changes during cells growth too. The maximum activity is observed after 5 to 6 days of culture to decrease after even though the cells are still in their exponential phase of growth. Nitrogenase activity increases with light intensity, what indicate a possible relation between photosynthetic and nitrogenase activities.     

Binding,uptake and expression of foreign DNA by cyanobacteria and isolated etioplasts

Discoveries of the uptake and expression of various Escherichia coli plasmids by the cyanobacterium Anacystis nidulans and isolated cumber etioplasts are reviewed. In particular, the binding and uptake of nick-translated ³²P-labeled plasmids and the expression of genes in the native plasmids are considered.Permeaplasts of A. nidulans 6301 and isolated EDTA-washed cucumber etioplasts exhibit binding and uptake of DNA that is unaffected by uncouplers of photophosphorylation or by dissipators of transmembrane proton graident. ATP inhibits both binding and udptake by permeaplasts or EDTA-washed etioplasts but the analog AMP-PNP (non-hydrolzable) is noninhibitory. With permeaplasts there is no effect of 20 mM Mg²⁺ (in the light) upon intake, whereas with EDTA-washed etioplasts, Mg²⁺ at the same concentration inhibits uptake as does 20 mM Ca²⁺.The transformation of A. nidulans 6301 to ampicillin-resistance by the plasmid pBR322 is much enhanced in permeaplasts. Indeed extracts of transformed cells catalyze the hydrolosis of the -lactam nitrocefin. Transfromation of A. nidulans to antibiotic resistance may also be achieved with the plasmids pHUB4 and pCH1. The effect of light on transformation of A. nidulans 6301 differs with different plasmids. In pBR322 transformants the expression of ribulose bisphosphate carboxylase-oxygenase (RuBisCO) is markedly elevated. In these transformants, the foreign plasmid replicates by a pathway involving chromosomal integration and dissociation.The plasmid pCS75, a derivative of pUC9 (and therefore of pBR322) containing a Pst1 insert carrying genes for the large and small (S) subunits of RuBisCO from A. nidulans, is taken up and expressed in EDTA-washed cucumber cotyledon etioplasts. Expression is evidenced by the hydrolysis of nitrocefin and immunoprecipitation of labeled S subunits of RuBisCO (utilizing etioplasts which have been labeled with ³⁵S-methionine after incubation with pCS75). The plasmid pUC9-CM carrying a cat gene is also expressed in cucumber etioplasts in a manner that demonstrates dependence both on the duration of etioplast washing by EDTA and plasmid concentration. Translation (as measured by ³⁵S-methionine incorporation) by EDTA-washed etioplasts increases with cotyledon greening. However the enhancement of translation by prior incubation of EDTA-washed plastids with pCS75 decreases to zero during 24hr of cotyledon greening. Results suggest that the expression of foreign DNA in plastids may depend critically upon their developmental state.Abbreviations AMP-PNP adenyl-5-yl imidodiphosphate - AP^r amplicillin resistance, cat-chloramphenicol acetyltransferase - RuBisCO ribulose bisphosphate carboxylase/oxygenase     

Catalysis of the electrochemical reduction of oxygen by bacteria isolated from electro-active biofilms formed in seawater

Biofilms formed in aerobic seawater on stainless steel are known to be efficient catalysts of the electrochemical reduction of oxygen. Based on their genomic analysis, seven bacterial isolates were selected and a cyclic voltammetry (CV) procedure was implemented to check their electrocatalytic activity towards oxygen reduction. All isolates exhibited close catalytic characteristics. Comparison between CVs recorded with glassy carbon and pyrolytic graphite electrodes showed that the catalytic effect was not correlated with the surface area covered by the cells. The low catalytic effect obtained with filtered isolates indicated the involvement of released redox compounds, which was confirmed by CVs performed with adsorbed iron-porphyrin. None of the isolates were able to form electro-active biofilms under constant polarization. The capacity to catalyze oxygen reduction is shown to be a widespread property among bacteria, but the property detected by CV does not necessarily confer the ability to achieve stable oxygen reduction under constant polarization.     

Characterization of polymicrobial biofilms obtained from saliva or carious lesions in dentin

Abstract

This study aimed to compare the formation of polymicrobial biofilms using carious dentin or saliva as inoculum for application in in vitro microbiological studies on caries research. For biofilm growth, combined samples of infected dentin or saliva from three donors were used. The biofilms were grown on glass coverslips, under a regimen of intermittent exposure (6?h day^?1) to 1% sucrose for 4?days. Total bacterial loads, as well as specific aciduric bacteria and mutans streptococci loads were quantified and correlated with biofilm acidogenicity and susceptibility to chlorhexidine. The data were evaluated using the Student’s-t, Mann Whitney and Kruskal-Wallis tests. The two biofilms showed similar microbial loads (total bacteria, aciduric bacteria and mutans streptococci) on day 4, and high acidogenicity after 48?h and were susceptible to chlorhexidine at different time intervals. In conclusion, both dentin and saliva can be used as an inoculum in in vitro studies of processes related to biofilm formation.     

Common evolutionary origin of planktonic and benthic nitrogen-fixing oscillatoriacean cyanobacteria from tropical oceans

The filamentous cyanobacteria belonging to the genus Hydrocoleum (Blennothrix) are among the most common mat-forming cyanobacteria in tropical oceans. We present here the evidence that these benthic cyanobacteria are morphologically and phylogenetically very close to the planktonic species of Trichodesmium. Genetic relationship was established independently with regard to sequences of the 16S rRNA gene, nifH gene, and phycocyanin and phycoerythrin intergenic spacers. The species of both genera formed a common distinct branch in phylogenetically reconstructed cyanobacterial trees, suggesting that the main constituents of cyanobacterial benthos and plankton have an early common origin and both represent major contributors to nitrogen budget of tropical oceans today as in the distant geological past.     

淡水有害底栖蓝藻研究进展

底栖蓝藻在全球淡水水域内广泛分布,在河流、湖泊、湿地、泉水水域等均有发现。相比于浮游蓝藻,底栖蓝藻因其隐蔽性、采样困难等关注度较低。针对近十几年有害底栖蓝藻不断过量繁殖的情况,本文对有害底栖蓝藻种类、主要的环境影响因子、有害次级代谢物及监测分析方法进行了总结概括。阐述了在有害底栖蓝藻生物量集聚过程中,光照、温度、营养盐、基质、水流等主要环境因子间的交互关联,并指出藻垫小生境内有害底栖蓝藻与微生物群落间作用的重要性。分析了不同属种有害底栖蓝藻的代谢物种类及影响代谢物产出的因素,总结了目前定性和定量分析有害底栖蓝藻的方法并指出其不足,对预测、定位高水平的有害底栖蓝藻提出了建议。本文为进一步研究有害底栖蓝藻异常增殖机制和有效防控方法提供了参考和借鉴。     

Characterization of lactobacilli isolated from caper berry fermentations

AIMS: To determine the metabolic and functional properties of lactobacilli isolated from caper fermentation. METHODS AND RESULTS: A collection of 58 lactobacilli from fermentation of caper berries (including species of Lactobacillus plantarum, Lactobacillus paraplantarum, Lactobacillus pentosus, Lactobacillus brevis and Lactobacillus fermentum) was studied. Strains were classified in different clusters according to sugar fermentation patterns. Most strains of L. plantarum (the predominant species in the fermentation) clustered in a single group. Analysis of enzymatic activities revealed a high incidence of leucine aminopeptidase, acid phosphatase, beta-galactosidase and beta-glucosidase among the different strains of lactobacilli. A high number of strains were able to degrade raffinose and stachyose. Phytase activity and bile salt hydrolase activity were only detected in certain strains of L. plantarum. CONCLUSIONS: Lactobacilli from caper fermentation are metabolically diverse, and some strains display functional properties of interest. SIGNIFICANCE AND IMPACT OF THE STUDY: Strains of lactobacilli with selected functional properties could be good candidates for future development of commercial starters for industrial caper fermentation.