Célia Alencar de Moraes

Characterizing the microbiota across the gastrointestinal tract of a Brazilian Nelore steer.

The gastrointestinal tracts (GIT) of herbivores harbor dense and diverse microbiota that has beneficial interactions with the host, particularly for agriculturally relevant animals like ruminants such as cattle. When assessing ruminant health, microbiological indicators are often derived from the rumen or feces. However, it is probable that ruminal and fecal microbiota do not reflect the microbial communities within the GIT of ruminants. To test this, we investigated the compartments of the GIT from a Brazilian Nelore steer and performed a 16S rRNA pyrosequencing analysis on the collected samples. Our results showed high intra-individual variation, with samples clustering according to their location in the GIT including the forestomach, small intestine, and large intestine. Although sequences related to the phyla Firmicutes and Bacteroidetes predominated all samples, there was a remarkable variation at the family level. Comparisons between the microbiota in the rumen, feces, and other GIT components showed distinct differences in microbial community. This work is the first intensive non-culture based GIT microbiota analysis for any ruminant and provides a framework for understanding how host microbiota impact the health of bovines.

Antibacterial activity of lactic cultures isolated of Italian salami

Lactic acid bacteria were isolated in the MRS, D-MRS and M17 modified media, during the processing of Italian salami, obtained from two processing plants, in the State of Parana. The 484 isolates were tested for their antibacterial activity against Listeria monocytogenes (Microbiology Laboratory-UFV), Staphylococcus aureus (ATCC 25923), Salmonella enteritidis (ATCC 13076) and Escherichia coli (ATCC 25922), by a deferred method. One hundred and fifteen isolates inhibited at least two of the pathogens. The isolates presented larger inhibition against L. monocytogenes. The 45 isolates with antagonistic action on the four indicator bacteria were identified by the system Biolog. Lactobacillus bifermentans prevailed among the isolates identified in MRS medium from the samples of the two processing plants.

Multidrug efflux systems in Gram-negative bacteria

Multidrug efflux mechanisms in bacteria contribute significantly to intrinsic and acquired resistance to antimicrobial agents. Genome analysis have confirmed the broad distribution of these systems in Gramnegative as well as in Gram-positive bacteria. Among resistance mechanisms, the multidrug efflux system or pump deserves special attention, since a cell that has acquired it can simultaneously diminish or even suppress the susceptibility to a wide range of antimicrobials. The efflux system is mediated by transport proteins which confer resistance to toxic compounds. In Gram-negative bacteria, a tripartite efflux system is necessary to expel the drug to the outer medium: a protein localized in the cytoplasmic membrane; another in the periplasmatic space (membrane fusion protein – MFP); and a third in the outer membrane (outer membrane factor – OMF). The drug transport is active, and depends either on the energy provided by ATP hydrolysis or is directly driven by the proton motive force. The transport proteins are grouped in families, according to the homology of the amino acid sequences and to similarity of mechanisms. Among Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa have most of the hitherto identified and studied multidrug efflux systems.

Influence of inhibitory compounds and minor sugars on xylitol production by Debaryomyces hansenii.

To obtain in-depth information on the overall metabolic behavior of the new good xylitol producer Debaryomyces hansenii UFV-170, batch bioconversions were carried out using semisynthetic media with compositions simulating those of typical acidic hemicellulose hydrolysates of sugarcane bagasse. For this purpose, we used media containing glucose (4.3–6.5 g/L), xylose (60.1–92.1 g/L), or arabinose (5.9–9.2 g/L), or binary or ternary mixtures of them in either the presence or absence of typical inhibitors of acidic hydrolysates, such as furfural (1.0–5.0 g/L), hydroxymethylfurfural (0.01–0.30 g/L), acetic acid (0.5–3.0 g/L), and vanillin (0.5–3.0 g/L). D. hansenii exhibited a good tolerance to high sugar concentrations as well as to the presence of inhibiting compounds in the fermentation media. It was able to produce xylitol only from xylose, arabitol from arabinose, and no glucitol from glucose. Arabinose metabolization was incomplete, while ethanol was mainly produced from glucose and, to a lesser less extent, from xylose and arabinose. The results suggest potential application of this strain in xyloseto-xylitol bioconversion from complex xylose media from lignocellulosic materials.

Diversity of endophytic bacteria in the fruits of Coffea canephora

Endophytic bacteria colonize the internal tissues of plants without causing infection or negative effects on their hosts. This study investigates the occurrence and diversity of culturable endophytic bacteria in the fruits of Coffea canephora at three developmental stages. Isolation and quantification were performed in R2A culture medium, and the diversity was established using molecular methods and analysis of fatty acid methyl esters (FAME). α- and γ-Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes were identified in the investigated community. Kocuria turfanensis and Pantoea vagans were identified as endophytes for the first time. Of the 18 species that were found, the following seven had not been previously described as endophytic in coffee fruits: Bacillus thuringiensis, Bacillus licheniformis, Agrobacterium tumefaciens, Escherichia coli, Enterobacter hormaechei, Chryseobacterium sp., and Ochrobactrum sp. The diversity of endophytic bacteria varied during the three developmental stages that were investigated, and the diversity was greatest in fruits during the green stage, during which Bacillus subtilis predominated. The number of Gram-positive bacteria was larger than the number of Gram-negative bacteria during the two earliest developmental stages, whereas their numbers were similar during the ripe stage. The diversity was lowest during the ripe stage, and Klebsiella oxytoca was the predominant species at this stage, probably due to the higher caffeine and sugar contents in the fruits.

Multidrug efflux systems in Escherichia coli and Enterobacter cloacae obtained from wholesome broiler carcasses

Members of the Enterobacteriaceae family are present in the intestines of man and animals as commensals or are important disease causing agents. Bacteria bearing multidrug efflux systems (MDR) are able to survive adverse ecological niches. Multiresistant Escherichia coli and Enterobacter cloacae isolates from wholesome broiler carcasses were investigated for the presence of MDR. Lowering of Minimal Inhibitory Concentration for antimicrobials in the presence of a proton-motive force (PMF) uncoupler was tested as a potential display of the MDR phenotype. PCR amplification of the genes encoding AcrA and AcrB, components of a MDR system was performed. Diversity of each species was ascertained by Pulsed-Field Gel Electrophoresis (PFGE) of DNA digested with endonuclease XbaI. For all the isolates, except E. coli 1 and E. cloacae 9, lowering of MIC or of the growth rate in the presence of antimicrobials was observed, indicating a PMF dependent resistance mechanism. Expected products of DNA amplification with acrAB derived primers was obtained with all E. coli strains and with two of the five E. cloacae strains. Dendrogram generated shows diverse pulsetypes, confirming the genetic diversity among the strains. An important issue and related public health is the fact that different models and mechanisms of antimicrobial resistance are present in a small number of non-pathogenic strains and isolated from the same origin. These may be sources of resistance genes to others microorganisms, among them, pathogenic strains.

Validation of a predictive model describing growth of Salmonella in enteral feeds

The growth of Salmonella enterica subs. enterica sorovar Typhimurium at 25°C was monitored in industrialized and hospital formulated enteral feeds and the results were used to validate the mathematical model of Salmonella growth presented by the Pathogen Modeling Program (PMP) 7.0 (USDA-USA). The generation time of Salmonella in enteral feeds ranged from 21 to 34.8 min and, the maximum growth rate (µmax) varied from 1.28 to 1.95 h-1, resulting in a population increase from 5 to 6 log10 cycles within 14 to 24 h incubation. Growth was faster in the hospital formulated feed containing vegetables and eggs. The growth kinetics parameters as lag phase; µmax and maximum population density (MPD) were similar to those predicted by the PMP 7.0, with exception of lag phase in enteral diet at pH 6.3. The results of this study validated the PMP 7.0 model for describe Salmonella growth in enteral feeds and demonstrates the appropriateness of use such model to determine the pathogen behavior in a wide range of storage conditions in this food.

Purification and characterization of two new cell-bound bioactive compounds produced by wild Lactococcus lactis strain

Abstract Novel compounds and innovative methods are required considering that antibiotic resistance has reached a crisis point. In the study, two cell‐bound antimicrobial compounds produced by Lactococcus lactis ID1.5 were isolated and partially characterized. Following purification by cationic exchange and a solid‐phase C18 column, antimicrobial activity was recovered after three runs of RPC using 60% (v/v) and 100% (v/v) of 2‐propanol for elution, suggesting that more than one antimicrobial compound were produced by L. lactis ID1.5, which were in this study called compounds AI and AII. The mass spectrum of AI and AII showed major intensity ions at m/z 1070.05 and 955.9 Da, respectively. The compound AI showed a spectrum of antimicrobial activity mainly against L. lactis species, while the organisms most sensitive to compound AII were Bacillus subtilis, Listeria innocua, Streptococcus pneumoniae and Pseudomonas aeruginosa. The antimicrobial activity of both compounds was suppressed by treatment with Tween 80. Nevertheless, both compounds showed high stability to heat and proteases treatments. The isolated compounds, AI and AII, showed distinct properties from other antimicrobial substances already reported as produced by L. lactis, and have a significant inhibitory effect against two clinically important respiratory pathogens.

EFEITO DE PROTETORES E TRATAMENTOS DE ESTRESSE NA SOBREVIVÊNCIA DE LACTOCOCCUS LACTIS SUBSP LACTIS AO CONGELAMENTO Effect of protective and stress treatment on survival of Lactococcus lactis subsp. lactis to freezing

O efeito de substâncias crioprotetoras e de tratamentos subletais de estresse foi avaliado no aumento da tolerância ao congelamento em Lactococcus lactis subsp lactis PD 6.9. Todas as substâncias crioprotetoras avaliadas aumentaram a sobrevivencia de L. lactis subsp lactis PD 6.9 a estocagem de 15 dias a - 20 oC. Entretanto, o leite desnatado reconstituido a 10 % foi o que conferiu maior protecao. Quanto a exposicao da suspensao de celulas a tratamentos subletais de estresse, a exposicao a 10 oC por 4 horas foi capaz de manter a sobrevivencia de L. lactis subsp lactis PD 6.9 estavel durante 70 dias de estocagem a - 20 oC. O tratamento a 40 oC por 30 minutos conferiu protecao durante 70 dias de estocagem a - 20 oC quando comparado com a suspensao de celulas que nao recebeu nenhum tratamento antes do congelamento. A aplicacao desses tratamentos e importante para assegurar a viabilidade de L. lactis subsp lactis PD 6.9 no decorrer do periodo de estocagem, e tambem de assegurar a qualidade sensorial e microbiologica de alimentos obtidos por processos de fermentacao.