Two-dimensional mapping of photopigment distribution and activity of Chloroflexus-like bacteria in a hypersaline microbial mat

Pigment analysis in an intact hypersaline microbial mat by hyperspectral imaging revealed very patchy and spatially uncorrelated distributions of photopigments Chl a and BChl a/c, which are characteristic photopigments for oxygenic (diatoms and cyanobacteria) and anoxygenic phototrophs (Chloroflexaceae). This finding is in contrast to the expectation that these biomarker pigments should be spatially correlated, as oxygenic phototrophs are thought to supply the Chloroflexaceae members with organic substrates for growth. We suggest that the heterogeneous occurrence is possibly due to sulfide, whose production by sulfate-reducing bacteria may be spatially heterogeneous in the partially oxic photic zone of the mat. We furthermore mapped the near-infra-red-light controlled respiration of Chloroflexaceae under light and dark conditions and found that Chloroflexaceae are responsible for a major part of oxygen consumption at the lower part of the oxic zone in the mat. The presence of Chloroflexaceae was further confirmed by FISH probe and 16S rRNA gene clone library analysis. We assume that species related to the genera Oscillochloris and 'Candidatus Chlorothrix', in contrast to those related to Chloroflexus and Roseiflexus, depend less on excreted photosynthates but more on the presence of free sulfide, which may explain their presence in deeper parts of the mat.     

Phylogenetic diversity and activity of aerobic heterotrophic bacteria from a hypersaline oil-polluted microbial mat

The diversity and function of aerobic heterotrophic bacteria (AHB) in cyanobacterial mats have been largely overlooked. We used culture-dependent and molecular techniques to explore the species diversity, degradative capacities and functional guilds of AHB in the photic layer (2mm) of an oil-polluted microbial mat from Saudi Arabia. Enrichment isolation was carried out at different salinities (5% and 12%) and temperatures (28 and 45 degrees C) and on various substrates (acetate, glycolate, Spirulina extract and crude oils). Counts of most probable number showed a numerical abundance of AHB in the range of 1.15-8.13x10(6) cellsg(-1) and suggested the presence of halotolerant and thermotolerant populations. Most of the 16S rRNA sequences of the obtained clones and isolates were phylogenetically affiliated to the groups Gammaproteobacteria, Bacteriodetes and Alphaproteobacteria. Groups like Deltaproteobacteria, Verrucomicrobia, Planctomycetes, Spirochaetes, Acidobacteria and Deinococcus-Thermus were only detected by cloning. The strains isolated on acetate and glycolate belonged to the genera Marinobacter, Halomonas, Roseobacter and Rhodobacter whereas the strains enriched on crude oil belonged to Marinobacter and Alcanivorax. Members of the Bacteriodetes group were only enriched on Spirulina extract indicating their specialization in the degradation of cyanobacterial dead cells. The substrate spectra of representative strains showed the ability of all AHB to metabolize cyanobacterial photosynthetic and fermentation products. However, the unique in situ conditions of the mat apparently favored the enrichment of versatile strains that grew on both the cyanobacterial exudates and the hydrocarbons. We conclude that AHB in cyanobacterial mats represent a diverse community that plays an important role in carbon-cycling within microbial mats.     

Biodiversity of moderately halophilic bacteria in hypersaline habitats in Egypt

Screening bacteria from different saline environments in Alexandria. Egypt, lead to the isolation of 76 Gram-negative and 14 Gram-positive moderately halophilic bacteria. The isolates were characterized taxonomically for a total of 155 features. These results were analyzed by numerical techniques using simple matching coefficient (SSM) and the clustering was achieved by the unweighed pair-group method of association (UPGMA). At 75% similarity level the Gram-negative bacteria were clustered in 7 phena in addition to one single isolate, whereas 4 phena represented the Gram-positive. Based on phenotypic characteristics, it is suggested that the Gram-negative bacteria belong to the genera Pseudoalteromonas, Flavobacterium, Chromohalobacter, Halomonas and Salegentibacter, in addition to the non-identified single isolate. The Gram-positive bacteria are proposed to belong to the genera Halobacillus, Salinicoccus, Staphylococcus and Tetragenococcus. This study provides the first publication on the biodiversity of moderately halophilic bacteria in saline environments in Alexandria, Egypt.     

Structural and functional features of methanotrophs from hypersaline and alkaline lakes

Ten strains of aerobic methanotrophic bacteria represented by halophilic neutrophiles or halotolerant alkaliphiles were isolated from saline and alkaline lakes of southeast Siberia, Mongolia, Africa, and North America. Based on analysis of the nucleotide sequences of 16S rRNA gene and the pmoA gene encoding particulate methane monooxygenase, the isolates were classified as Methylomicrobium alcaliphilum, Methylomicrobium buryatense, and Methylobacter marinus. All strains of the genus Methylomicrobium were shown to synthesize glycoprotein S-layers located on the cell surface with hexagonal symmetry (p6) as a monolayer of cup-shaped structures or fine “inverted” conical structures and as plates consisting of protein subunits with inclined (p2) symmetry. During adaptation to the high salinity of the medium, isolated methanotrophs synthesize osmoprotectants: ectoine, sucrose, and glutamate. The ectC gene encoding ectoine synthase (EctC) was identified in six methanotrophic strains. Phylogenetic analysis of translated amino acid sequence of the ectC gene fragment suggests lateral transfer of the genes of ectoine synthesis as the most probable way for methanotrophs to acquire resistance to high external salinity.     

The role of anti-lactoferrin activity of bacteria in their persistence

The role of anti-lactoferrin activity (ALfA) of bacteria in the persistence phenomenon, i.e. long survival of a causative agent in a host body, was studied in experimental staphylococcal infection. In experimental animals infected with isogenic clones of Staphylococcus aureus with different level of ALfA, longer terms were noted in bacterial recovery of staphylococci with this ability. Analysis on the occurrence and level of ALfA in clinical isolates of bacteria, isolated from different forms of infectious process, confirmed the significance of this sign in the persistence of a causative agent. High values of penetrance and expression of ALfA in bacteria were revealed in strains of microorganisms, isolated from chronic inflammatory diseases and from bacterial carriers.     

Number,biomass, and activity of bacteria in the water of overgrowths and periphyton on higher aquatic plants

The results of studies on the production-destruction processes in the water of overgrowths and periphyton of higher aquatic plants in the Volzhskii Reach of the Rybinsk Reservoir are presented. The studied aspects included the level of quantitative development and the activity of bacterioplankton of various ecological groups of macrophytes. It was revealed that the processes of destruction of organic matter under the impact of bacteria in the macrophyte periphyton prevail over the rate of primary production in algal periphyton. The production of periphyton and planktic bacteria per 1 m² of macrophyte overgrowth is calculated.     

Electricity generation by anaerobic bacteria and anoxic sediments from hypersaline soda lakes

Anaerobic bacteria and anoxic sediments from soda lakes produced electricity in microbial fuel cells (MFCs). No electricity was generated in the absence of bacterial metabolism. Arsenate respiring bacteria isolated from moderately hypersaline Mono Lake (Bacillus selenitireducens), and salt-saturated Searles Lake, CA (strain SLAS-1) oxidized lactate using arsenate as the electron acceptor. However, these cultures grew equally well without added arsenate using the MFC anode as their electron acceptor, and in the process oxidized lactate more efficiently. The decrease in electricity generation by consumption of added alternative electron acceptors (i.e. arsenate) which competed with the anode for available electrons proved to be a useful indicator of microbial activity and hence life in the fuel cells. Shaken sediment slurries from these two lakes also generated electricity, with or without added lactate. Hydrogen added to sediment slurries was consumed but did not stimulate electricity production. Finally, electricity was generated in statically incubated “intact” sediment cores from these lakes. More power was produced in sediment from Mono Lake than from Searles Lake, however microbial fuel cells could detect low levels of metabolism operating under moderate and extreme conditions of salt stress.     

Unexplored reservoirs of pathogenic bacteria: protozoa and biofilms

In the natural, industrial, hospital and domestic environments, there are numerous phenotypes of pathogenic microorganisms, which vary considerably in chemical, physical and biological properties. A link exists between survival, resistance and virulence. In particular, surface-adherent biofilms and bacteria living within protozoa pose potential health problems that are unrecognized by conventional laboratory culture methods.     

Epiphytic bacteria biodiversity in Brazilian Cerrado fruit and their cellulolytic activity potential

The Cerrado is the second largest Brazilian biome, yet little is known about its wild fauna, flora and microbiota. This work aimed to identify epiphytic bacteria present in fruits native to three different regions of the Cerrado and to select cellulase-producing bacteria. Culture-dependent and culture-independent (PCR-DGGE) methods were used to characterize the microbiota from 32 native Cerrado fruits, and the selection of cellulase-producing bacteria was performed by a semi-quantitative test on carboxymethylcellulose agar medium. Analysis of the 16S rRNA gene sequences of 69 profile representatives showed that the isolates belonged to 29 bacterial genera (Arthrobacter, Bacillus, Paenibacillus, Pseudomonas, Serratia, Staphylococcus, Streptomyces, Enterobacter, Microbacterium, Aerococcus, Bradyrhizobium, Methylobacterium, Erwinia, Pantoea, Acidithiobacillus, Ochrobactrum, Stenotrophomonas, Curtobacterium, Clostridium, Lactobacillus, Xanthomonas, Delftia, Klebsiella, Enterococcus, Burkholderia, Escherichia, Streptococcus, Citrobacter and Achromobacter). Species in the genera Methylobacterium, Stenotrophomonas, Clostridium, Pantoea and Enterobacter were detected by both culture-dependent and culture-independent methods. The species Lactobacillus fermentum, Acinetobacter sp. and Methylomonas methanica were detected only by PCR-DGGE. Additionally, 30 % (178 isolates) of the bacteria tested were able to produce cellulase. The best producers belonged to the genera Bacillus, Streptomyces, Paenibacillus, Enterobacter and Burkholderia, indicating that this ecosystem could be an attractive source for the study of novel enzymes.     

Microbial biomass and activity distribution in an anoxic, hypersaline basin

The evaluation of an improved wipe-rinse technique for the bioassay of large areas was undertaken due to inherent inadequacies in the cotton swab-rinse technique to which assay of spacecraft is currently restricted. Four types of contamination control cloths were initially tested. A polyester-bonded cloth (PBC) was selected for further evaluation because of its superior efficiency and handling characteristics. Results from comparative tests with PBC and cotton swabs on simulated spacecraft surfaces indicated a significantly higher recovery efficiency for the PBC than for the cotton (90.4 versus 75.2%). Of the sampling areas sites studied, PBC was found to be most effective on surface areas not exceeding 0.74 m2 (8.0 feet 2).     

Isolation and identification of moderately halophilic bacteria producing hydrolytic enzymes from the largest hypersaline playa in Iran

Iran has many hypersaline environments, both the permanent and seasonal ones. One of the seasonal hypersaline lakes in the central desert zone is Aran-Bidgol Lake in which microbial diversity has not been characterized, thus the potential usage of this microbial community in biotechnology remained unknown. In this study, screening the halophilic hydrolytic enzyme-producing bacteria from different areas of this lake led to isolation of 61 gram-positive and 22 gram-negative moderately halophilic bacteria. These bacterial isolates were shown to produce a wide variety of hydrolytic enzymes including DNase, inulinase, amylase, lipase, pectinase, protease, chitinase, pullulanase, cellulase, and xylanase. The most common enzymes were DNase and inulinase in gram-positive bacteria, lipase in gram-negative bacteria, and pullulanase and cellulase in gram-positive cocci. Interestingly, combined hydrolytic activates were observed in some isolates. According to their phenotypic characteristics and comparative partial 16S rRNA sequence analysis, the moderately halophilic strains belonged to the genera Halobacillus, Thalassobacillus, Bacillus, Salinicoccus, Idiomarina, Salicola, and Halomonas.     

Holy water fonts are reservoirs of pathogenic bacteria

The holy water fonts from the churches of Seville, Spain have a strong bacterial contamination. Coliforms, Enterobacteriaceae and other pathogenic bacteria are widely represented in the fonts investigated. Thirty out of the 37 different species isolated from holy waters are known human pathogens. The high bacterial contamination is related to human skin transmission and, probably, to misuse of the water.     

Numerical taxonomy of heavy metal-tolerant nonhalophilic bacteria isolated from hypersaline environments.

A total of 232 metal-tolerant bacterial strains were isolated from water and sediment samples collected in different hypersaline environments located in Cádiz, Huelva and Morón de la Frontera (Spain). They were isolated on a medium containing mercury, chromium, cadmium, copper or zinc. These halotolerant isolates were analyzed by numerical taxonomy techniques by using the simple matching (SSM) and Jaccard (SJ) coefficients; clustering was achieved using the unweighted pair group method with averages (UPGMA) algorithm. At the 81% and 83% similarity level, different numbers of phenons were obtained for Gram-negative and Gram-positive halotolerant microorganisms. Most of the 48 Gram-negative metal-tolerant strains studied were grouped into nine phenons, representing the genera Pseudoalteromonas, Alteromonas, Xanthomonas, Pseudomonas, Alcaligenes and Enterobacteria. The 72 Gram-positive metal-tolerant strains grouped into eight phenons, with only 15 strains left unassigned. Most of the isolates were assigned to the genus Bacillus (seven phenons), and one phenon comprised microorganisms with phenotypic characteristics similar to those of the genus Celullomonas.     

The hemagglutinating activity of bacteria in the genus Klebsiella and the morphofunctional characteristics of their fimbriae]

The hemagglutinating activity of 77 Klebsiella strains from the international collection, grown in a culture medium prepared on the basis of soy-bean flour enzymatic hydrolysate, was studied. These strains could be divided into four groups according to their capacity for synthesizing different types of hemagglutinins on their surface: 2 strains carried mannose-sensitive hemagglutinins, 18 strains had mannose-resistant K-type hemagglutinins, 48 strains exhibited the signs indicating the presence of both mannose-sensitive and mannose-resistant hemagglutinins, and 9 strains showed no hemagglutinating activity. The hemagglutinating activity of strains K-74, K-79, K-80, K-81 and K-82 was characterized. Of the reference strains under study, 22 strains were found to have mannose-resistant hemagglutinating activity with respect to fresh chick red blood cells. The occurrence of hemagglutinins in Klebsiella was shown to depend on the temperature of cultivation and the consistency of the culture medium. The formation of large-sized capsules in Klebsiella grown in the Werfel-Fergusson medium with a considerable content of saccharose was shown to cause the absorption of their fimbrial structures by the capsular substance and, as a consequence, the suppression of their hemagglutinating activity.     

Stereoelectronic features of the cinchona alkaloids determine their differential antimalarial activity.

For most potent antimalarial activity, the cinchona alkaloids appear to require certain electronic features, particularly a sufficiently acidic hydroxyl proton and an electric field direction pointing from the aliphatic nitrogen atom towards the quinoline ring. These observations are the result of an analysis of molecular electronic properties of eight cinchona alkaloids and an in vivo metabolite calculated using ab initio 3-21G quantum chemical methods in relation to their in vitro IC50 values against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum parasites. The purpose is to provide a profile of the electronic characteristics necessary for potent antimalarial activity for use in the design of new antimalarial agents and to gain insight into the mechanistic path for antimalarial activity. Distinguishing features of the weakly active epiquinine and epiquinidine include a higher dipole moment, a different direction of the electric field, a greater intrinsic nucleophilicity, lower acidity of the hydroxyl proton, a lesser electron affinity of the lowest unoccupied molecular orbitals, and a higher proton affinity than the active cinchona alkaloids. A moderately potent quinine metabolite possesses some, but not all, of the same electronic features as the most potent cinchona alkaloids. Both the positioning of the hydroxyl and aliphatic amine groups and their electronic features appear to play a crucial role for antimalarial potency of the cinchona alkaloids, most likely by controlling the ability of these groups to form effective intermolecular hydrogen bonds.