Field response of rice paddy crop to Azospirillum inoculation: physiology of rhizosphere bacterial communities and the genetic diversity of endophytic bacteria in different parts of the plants

The response of rice plants to the application of inoculant containing two Azospirillum brasilense strains was studied under field conditions. The experiment was performed as three treatments with four replicates in randomized complete blocks arranged as plots of 60 m² in an area on a Vertic Argiudol soil type in the province of Entre Ríos, Argentina. The bacterial rhizosphere community and also the diazotrophic isolates obtained from control and inoculated rice plants were analyzed in relation to their physiology and biological nitrogen fixation (BNF). The MPN of diazotrophs in the rhizosphere varied during the ontogenic cycle. The patterns of distribution of the microbial physiological activities obtained by principal component analysis of community-level physiological profiles (CLPP) showed differences in the utilization of carbon sources by the rhizosphere communities among treatments. Although the analyses of DGGE 16S and nifH profiles have not indicated that the inoculation influenced the genetic diversity of bacterial communities among treatments, they revealed that the banding profiles were altered in different parts of the rice plant by each Azospirillum inoculation treatment. These observations suggest that physiological responses of plant tissues to the inoculation may have occurred. According to agronomic parameters of each treatment, the Azospirillum inoculation increased aerial biomass at the tillering and grain-filling stages. Although the N content accumulated in rice plants increased by 16 and 50 kg ha^?1, the BNF contribution could not be estimated under our experimental conditions by the ¹⁵N balance technique. Based on this field inoculation experiment to rice plants, it is noteworthy that our data suggest that due to Azospirillum inoculation the increase of total N accumulated in rice plants could be a tool to help farmers to improve production and maintain high input of plant residues, providing more organic matter to the soil and guaranteeing sustainability of the system.     

Floral ontogeny in Dipterygeae (Fabaceae) reveals new insights into one of the earliest branching tribes in papilionoid legumes

Flowers of Dipterygeae (Fabaceae, Papilionoideae) exhibit an unusual petaloid calyx. The two adaxial sepals are large and petaloid, and the three abaxial sepals form a three‐toothed lobe. The goal of this study was to elucidate the ontogenetic pathways of this peculiar calyx in light of the floral development of the three genera that comprise the tribe. Floral buds of Dipteryx alata, Pterodon pubescens and Taralea oppositifolia were analysed using scanning electron microscopy and light microscopy. The order of bracteole and sepal initiation varies among the species. The androecium is asymmetric. The carpel cleft is positioned to the right or to the left, and is opposite the adaxial antepetalous stamen. The peculiarity of the calyx becomes noticeable in the intermediate stages of floral development. It results from the differential growth of the sepal primordia, in which the abaxial and lateral primordia remain diminutive during floral development, compared with the adaxial ones that enlarge and elongate. Bracteoles, abaxial sepals, petals and anthers are appendiculate, except in T. oppositifolia, in which the appendices were not found in bracteoles or anthers. These appendices comprise secretory canals or cavities. Considering that the ontogenetic pathway for the formation of the petaloid calyx is similar and exclusive for Dipterygeae, it might be a potential synapomorphy for the group, with the presence of secretory canals in the appendices of abaxial and lateral sepals and petals. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 529–550.     

Dengue in the State of Rio de Janeiro, Brazil, 1986-1998.

This paper presents epidemiological, laboratory, and clinical data on 12 years of dengue virus activity in the State of Rio de Janeiro from the time the disease was first confirmed virologically in April 1986 through April 1998. DEN-1 and DEN-2 viruses are the serotypes circulating in the state and were responsible for the epidemics reported during the last 12 years. The results published here show both the impact of dengue virus infections on the population and laboratory advances that have improved dengue diagnosis.     

Saccharomyces bacillaris is not a synonym of Candida stellata: reinstatement as Starmerella bacillaris comb. nov.

Torulopsis bacillaris (Kroemer and Krumbholz) Lodder (basionym Saccharomyces bacillaris Kroemer and Krumbholz) was frequently detected in oenological works on yeast ecology conducted in the mid-1950s in different wine regions of the world, before its unification with Torulopsis stellata (Kroemer and Krumbholz) Lodder. Most of the phenotypic characteristics pointed out for T. bacillaris are currently attributed to Candida zemplinina Sipiczki. In the present work isoenzyme profiles and rDNA restriction profiles of the neotype of S. bacillaris from two yeast culture collections (CBS 843 and PYCC 3044) and of the type strain of C. zemplinina (CBS 9494) were determined and similar profiles were detected. Moreover, the sequences of the D1/D2 region of the 26S rRNA gene of the three strains were 100 % identical. Different profiles were observed for the type strain of C. stellata (CBS 157) both for isoenzyme and rDNA restriction analysis and only 91 % similarity was found between the D1/D2 sequence of this strain and that of the neotype of S. bacillaris. In view of the newly obtained data and the fact that all above-mentioned species belong to the Starmerella clade, only distantly related to Candida tropicalis (the type species of the genus), S. bacillaris is hereby reinstated as Starmerella bacillaris comb. nov., with C. zemplinina as an obligate synonym.     

Antimicrobial and antiadhesive properties of a biosurfactant isolated from Lactobacillus paracasei ssp. paracasei A20

Aims: The aim of this study was to determine the antimicrobial and antiadhesive properties of a biosurfactant isolated from Lactobacillus paracasei ssp. paracasei A20 against several micro‐organisms, including Gram‐positive and Gram‐negative bacteria, yeasts and filamentous fungi. Methods and Results: Antimicrobial and antiadhesive activities were determined using the microdilution method in 96‐well culture plates. The biosurfactant showed antimicrobial activity against all the micro‐organisms assayed, and for twelve of the eighteen micro‐organisms (including the pathogenic Candida albicans, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus agalactiae), the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were achieved for biosurfactant concentrations between 25 and 50 mg ml^?1. Furthermore, the biosurfactant showed antiadhesive activity against most of the micro‐organisms evaluated. Conclusions: As far as we know, this is the first compilation of data on antimicrobial and antiadhesive activities of biosurfactants obtained from lactobacilli against such a broad group of micro‐organisms. Although the antiadhesive activity of biosurfactants isolated from lactic acid bacteria has been widely reported, their antimicrobial activity is quite unusual and has been described only in a few strains. Significance and Impact of the Study: The results obtained in this study regarding the antimicrobial and antiadhesive properties of this biosurfactant opens future prospects for its use against micro‐organisms responsible for diseases and infections in the urinary, vaginal and gastrointestinal tracts, as well as in the skin, making it a suitable alternative to conventional antibiotics.     

Sulfur starvation in Lemna leads to degradation of ribulose-bisphosphate carboxylase without plant death.

Little is known about the degradation of the most abundant protein in nature, ribulose-bisphosphate carboxylase (RuBP carboxylase, EC 4.1.1.39), probably reflecting the fact that no stress situation has been identified capable of causing extensive RuBP carboxylase degradation without causing the death of the plant. We have subjected plants of Lemna minor L. to a variety of stress situations, nutritive deficiencies in particular, and have found a single condition--sulfur starvation--that caused almost complete degradation of RuBP carboxylase without causing plant death. Moreover, the enzyme was preferentially degraded under these conditions. However, when the plants were deprived of calcium, no RuBP carboxylase degradation was observed. Instead, the enzyme was oxidized and polymerized into high molecular mass aggregates. On the other hand, RuBP carboxylase shows an extreme stability when Lemna is deprived of some macronutrients (e.g. nitrogen, phosphorus, potassium, and magnesium) probably reflecting that this plant had to evolve in a way to cope with frequent shortages of such elements. The implications of these data for the role of RuBP carboxylase as a leaf storage protein are discussed.     

Application of Multivariate Analysis for the Selection of Candidates for Biological Control Agents

A survey of natural enemies ofSenna obtusifolia(Leguminosae: Cesalpinaceae) was made in 46 localities in Brazil. Twenty-one preselected insect species were used in a multivariate analysis in a search for potential biocontrol agents, based on frequency of occurrence of each species, degree of insect/host association, and damage level. Insect communities were organized in a binary matrix (presence/absence of the species); measures of distance and similarities were based on the Jaccard coefficient, and cluster analysis was then conducted. Construction of a dendogram showed similarities among geographically close localities where phenological stages of sicklepod plants were similar. Analysis of correspondence based on the correlation matrix showed that Eigen values of the three first axes explain only 40.1% of the observed variation. Correlation among the scores produced by species Eigenvectors in each locality on axis 1 and the latitude, altitude, and phenological stage showed that only phenological stage was correlated (r = 0.45,P = 0.02). The results indicate that weather will not be a limiting factor for the establishment of these insect species in an environmental gradient similar to that of the surveyed area (12 to 22° latitude and 6 to 1200 m altitude). Distribution in the ordinal space of axes 1 and 2 showed thatAgrilus oceanicum(Buprestidae),Fundella argentina(Pyralidae),Thyphedanus undulatus(Hesperidae), andPhoebis sennae(Pieridae) are grouped and separated from the others in axis 2, suggesting that these species co-occur with each other. Based on their feeding guilds, multiple introduction of these species can be considered. Multivariate analysis showed potential to be used as an additional tool to help in the selection of candidates for biocontrol agents.     

Effect of culture conditions on the NADH/NAD ratio and total amounts of NAD(H) in chemostat cultures of Enterococcus faecalis NCTC 775

Abstract Enterococcus faecalis was grown in chemostat culture on various energy sources at dilution rates ranging from 0.05 h⁻¹ to 0.5 h⁻¹, under both aerobic and anaerobic conditions. NADH/NAD ratios and total nicotinamide adenine dinucleotide pool size (NAD(H)) were determined. It was found that the NADH/NAD ratio was controlled by the steady state product concentrations rather than by the degree of reduction of the energy source. Highest ratios were observed when NADH was reoxidized via ethanol formation, whereas in aerobic cultures, in which predominantly acetate was produced and oxidation of NADH occurred via the NADH oxidase, ratios were lowest. Addition of ethanol to the medium resulted in an increase of the NADH/NAD ratio, both aerobically and anaerobically. The total amount of NAD(H) was found to be influenced by the culture conditions. Under anaerobic conditions, the NADH oxidation (NAD reduction) rate appeared to correlate with the total amount of nicotinamide nucleotides. In contrast, no effect of the culture conditions on the total amount of NAD(H) was observed in aerobically grown cells.