Nonheterocytous cyanobacteria from Brazilian saline‐alkaline lakes

Saline‐alkaline lakes are extreme environments that limit the establishment and development of life. The Nhecolândia, a subregion of the Pantanal wetland in Brazil, is characterized by the existence of ~500 saline‐alkaline lakes, which support an underexplored and rich diversity of microorganisms. In this study, unicellular and homocytous cyanobacteria from five saline‐alkaline lakes were accessed by culture‐dependent approaches. Morphological evaluation and analyses of near complete sequences (~1400 nt) of the 16S rRNA genes were applied for phylogenetic and taxonomic placement. This polyphasic approach allowed for the determination of the taxonomic position of the isolated strains into the following genera: Cyanobacterium, Geminocystis, Phormidium, Leptolyngbya, Limnothrix, and Nodosilinea. In addition, fourteen Pseudanabaenales and Oscillatoriales representatives of putative novel taxa were found. These sequences fell into five new clades that could correspond to new generic units of the Pseudanabaenaceae and Phormidiaceae families.     

The bacterial diversity in a Brazilian non-disturbed mangrove sediment

The bacterial diversity present in sediments of a well-preserved mangrove in Ilha do Cardoso, located in the extreme south of São Paulo State coastline, Brazil, was assessed using culture-independent molecular approaches (denaturing gradient gel electrophoresis (DGGE) and analysis of 166 sequences from a clone library). The data revealed a bacterial community dominated by Alphaproteobacteria (40.36% of clones), Gammaproteobacteria (19.28% of clones) and Acidobacteria (27.71% of clones), while minor components of the assemblage were affiliated to Betaproteobacteria, Deltaproteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. The clustering and redundancy analysis (RDA) based on DGGE were used to determine factors that modulate the diversity of bacterial communities in mangroves, such as depth, seasonal fluctuations, and locations over a transect area from the sea to the land. Profiles of specific DGGE gels showed that both dominant (‘universal’ Bacteria and Alphaproteobacteria) and low-density bacterial communities (Betaproteobacteria and Actinobacteria) are responsive to shifts in environmental factors. The location within the mangrove was determinant for all fractions of the community studied, whereas season was significant for Bacteria, Alphaproteobacteria, and Betaproteobacteria and sample depth determined the diversity of Alphaproteobacteria and Actinobacteria.     

Seed germination and seedling growth of two Pseudobombax species (Malvaceae) with contrasting habitats from Brazilian Cerrado

Pseudobombax tomentosum and P. longiflorum are common trees in the Cerrado region, but the former species is more common in forest edges while the later is present in open cerrado areas. This work aimed to investigate differences in seed germination and seedling growth in these species, from seed collected from Cerrado areas in Central Brazil. For this, a seed germination experiment was designed and included four replicates with 25 seeds per species; seeds were randomly distributed in the germination chamber. To evaluate initial seedling growth, seedlings height was measured up to 67 days after seedling emergence; besides, some of these seedlings were grown for biomass evaluation during nine months. Results showed that seeds of the two species had the same germinability (near 100%) and mean germination time (ca. 12 days). However, P. longiflorum showed a more spread seed germination through time, with higher values of coefficient of variation in germination time and uncertainty index; and lower values of synchronization than P. tomentosum. The two species showed basically the same growth pattern, but lower values for height of apical meristem, diameter of underground structures (mostly roots), dry mass of shoots, underground structure and total mass of seedlings in P. tomentosum were obtained, compared to P. longiflorum. Both species allocated more dry mass to underground structures in detriment of shoot. This probably allows resprouting behavior which prevents hydric stress and detrimental fire action typical of the open Cerrado areas.     

Concurrent class analysis identifies discriminatory variables from metabolomics data on isovaleric acidemia

Metabolomics data are typically complex and high dimensional. Multivariate dimension-reducing techniques have thus been developed for analysing metabolomics data to disclose underlying relationships, with principal component analysis (PCA) as the technique mostly applied. Despite its widespread use in metabolomics, PCA has shortcomings that limit its applicability. Several approaches have been made to overcome these limitations and we describe an advanced disjoint PCA (DPCA) model, termed concurrent class analysis and abbreviated as CONCA. CONCA is a new model, and is unique in linking DPCA models to a traditional PCA model. This is accomplished by restructuring the input data matrix, applying DPCA group models to the restructured data, and combining the DPCA models in order to replicate a traditional PCA. We applied the CONCA model to a metabolomics data set on isovaleric acidaemia (IVA), a rare inherited metabolic disorder. The outcome showed that three of the variables with high discrimination value identified through the CONCA analysis are prominent organic acid biomarkers for IVA. Moreover, three further minor metabolites associated with the disease, and two as a consequence of treatment, were likewise identified as important discriminatory variables. The benefit of the CONCA model thus is its ability to disclose information concerning each individual group and to identify the variables important in discrimination (VIDs) which are also responsible for group separation.     

Amino acid precursors for the detection of transketolase activity in Escherichia coli auxotrophs

Probes were developed for the in vivo detection of transketolase activity by the use of a complementation assay in Escherichia coli auxotrophs They combine the d-threo ketose moiety recognised by transketolase and the side chain of leucine or methionine. These compounds were donor substrates of yeast transketolase leading to the release of the corresponding α-hydroxyaldehydes which could be converted in E. coli by a cascade of reactions into leucine or methionine required for cellular growth.     

Production of <Emphasis Type="Italic">Pleurotus sajor-caju</Emphasis> strain PS-2001 biomass in submerged culture

Mushrooms or fruiting bodies of many basidiomycetes are commonly produced in solid-state fermentation, generally after 20-60 days of growth. However, it is also possible to produce biomass from these fungi, in submerged fermentation in shorter time. This work was aimed at evaluating biomass production with the basidiomycete Pleurotus sajor-caju, in a submerged process and to determine the proportion of chemical components of this biomass. Initially, an optimization of the culture medium was done to produce a faster growth of microbial mass by changing the concentrations of ammonium sulfate, soy protein and yeast extract. Using the optimized culture medium, values of approximately 5.5 g L(-1) of biomass in a medium with 10 g L(-1) of glucose were attained. When the optimized culture medium was tested in a 5-L stirred tank bioreactor, using 10 g L(-1) of glucose or sucrose as carbon source, values of 8.18 and 5.94 g L(-1) of biomass concentration were obtained, respectively. In the medium with glucose, high yields (0.82 g g(-1)) and productivity of 0.085 g L(-1) h(-1) were obtained. The exopolysaccharide content (1.58 g dry matter L(-1)) in the culture was higher in the fermentation with sucrose. The nutritional composition of the biomass obtained in the submerged fermentation was similar to that of the fruiting body in terms of quantities of total carbohydrates, ash and calories, but total fat and protein were higher.     

Effect of a highly concentrated lipopeptide extract of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> on fungal and bacterial cells

Lipopeptides produced by Bacillus subtilis are known for their high antifungal activity. The aim of this paper is to show that at high concentration they can damage the surface ultra-structure of bacterial cells. A lipopeptide extract containing iturin and surfactin (5 mg mL⁻¹) was prepared after isolation from B. subtilis (strain OG) by solid phase extraction. Analysis by atomic force microscope (AFM) showed that upon evaporation, lipopeptides form large aggregates (0.1–0.2 μm²) on the substrates silicon and mica. When the same solution is incubated with fungi and bacteria and the system is allowed to evaporate, dramatic changes are observed on the cells. AFM micrographs show disintegration of the hyphae of Phomopsis phaseoli and the cell walls of Xanthomonas campestris and X. axonopodis. Collapses to fungal and bacterial cells may be a result of formation of pores triggered by micelles and lamellar structures, which are formed above the critical micelar concentration of lipopeptides. As observed for P. phaseoli, the process involves binding, solubilization, and formation of novel structures in which cell wall components are solubilized within lipopeptide vesicles. This is the first report presenting evidences that vesicles of uncharged and negatively charged lipopeptides can alter the morphology of gram-negative bacteria.     

Fermentation of hexoses and pentoses from sugarcane bagasse hydrolysates into ethanol by Spathaspora hagerdaliae

The present study evaluated 13 strains of yeast for ethanol and xylitol production from xylose. Among them, Spathaspora hagerdaliae UFMG-CM-Y303 produced ethanol yields (Y_P/S) of 0.25 g g^− 1 and 0.39 g g^− 1 under aerobic and microaerophilic conditions, respectively, from a mixture of glucose and xylose in flasks. A pH of 5.0 and an inoculum of 3.0 × 10⁸ cells mL^− 1r resulted in the highest ethanol yields. These conditions were tested in a bioreactor for fermenting a medium containing an enzymatic hydrolysate of sugarcane bagasse with 15.5 g L^− 1 of glucose and 3 g L^− 1 of xylose, and achieved a Y_P/S of 0.47 g g^− 1, in relation to total available sugar. These results suggest that S. hagerdaliae UFMG-CM-Y303 has potential for use in second-generation ethanol studies.