RESUMO
Biofilm Formation is a survival strategy for microorganisms to adapt to their environment. Microbial cells in biofilm become tolerant and resistant to antibiotics and immune responses, increasing the difficulties for the clinical treatment of microbial infections. The surface chemistry and the micro/nano-topography of solid interfaces play a major role in mediating microorganism activity and adhesion. The effect of the surface chemical composition and topography on the adhesion and viability of Pseudomonas aeruginosa was studied. Polymeric (polyethylene terephthalate) surfaces were covered with a conducting polymer (polyaniline, PANI) film by in-situ polymerization and microstructured by Direct Laser Interference Patterning (DLIP). The viability of Pseudomonas aeruginosa on the different surfaces was investigated. The physicochemical properties of the surfaces were characterized by water contact angle measurements, scanning electron microscopy and atomic force microscopy. Bacterial biofilms were imaged by atomic force and scanning electron microscopies. The bacterial viability decreased on PANI compared with the substrate (polyethylene terephthalate) and it decreased even more upon micro-structuring the PANI films. In addition, the biofilm reduction could be improved using polymers with different chemical composition and/or the same polymer with different topographies. Both methods presented diminish the bacterial attachment and biofilm formation. These findings present a high impact related to materials for biomedical engineer applications regarding medical devices, as prostheses or catheters.
Assuntos
Compostos de Anilina/química , Biofilmes , Pseudomonas aeruginosa/fisiologia , Aderência Bacteriana , Materiais Biocompatíveis/química , Catéteres , Farmacorresistência Bacteriana , Equipamentos e Provisões , Violeta Genciana/química , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Microscopia de Fluorescência , Polietilenotereftalatos/química , Propriedades de SuperfícieRESUMO
AIMS: We study the Azospirillum brasilense tolerance to water deficit and the dynamics of adaptive process at the level of the membrane. METHODS AND RESULTS: Azospirillum brasilense was exposed to polyethylene glycol (PEG) growth and PEG shock. Tolerance, phospholipids and fatty acid (FA) composition and membrane fluidity were determined. Azospirillum brasilense was able to grow in the presence of PEG; however, its viability was reduced. Cells grown with PEG showed membrane fluidity similar to those grown without, the lipid composition was modified, increasing phosphatidylcholine and decreasing phosphatidylethanolamine amounts. The unsaturation FAs degree was reduced. The dynamics of the adaptive response revealed a decrease in fluidity 20 min after the addition of PEG, indicating that the PEG has a fluidizing effect on the hydrophobic region of the cell membrane. Fluidity returned to initial values after 60 min of PEG exposure. CONCLUSION: Azospirillum brasilense is able to perceive osmotic changes by changing the membrane fluidity. This effect is offset by changes in the composition of membrane phospholipid and FA, contributing to the homeostasis of membrane fluidity under water deficit. SIGNIFICANCE AND IMPACT OF THE STUDY: This knowledge can be used to develop new Azospirillum brasilense formulations showing an adapted membrane to water deficit.
Assuntos
Azospirillum brasilense/metabolismo , Membrana Celular/química , Água/metabolismo , Azospirillum brasilense/química , Membrana Celular/metabolismo , Ácidos Graxos/análise , Ácidos Graxos/metabolismo , Fluidez de Membrana , Fosfolipídeos/análise , Fosfolipídeos/metabolismo , Água/análiseRESUMO
AIMS: The aim of this work was to clarify the mechanism of monounsaturated fatty acid (MUFA) synthesis in Bradyrhizobium TAL1000 and the effect of high temperature on this process. METHODS AND RESULTS: Bradyrhizobium TAL1000 was exposed to a high growth temperature and heat shock, and fatty acid composition and synthesis were tested. To determine the presence of a possible desaturase, a gene was identify and overexpressed in Escherichia coli. The desaturase expression was detected by RT-PCR and Western blotting. In B. TAL1000, an aerobic mechanism for MUFA synthesis was detected. Desaturation was decreased by high growth temperature and by heat shock. Two hours of exposure to 37°C were required for the change in MUFA levels. A potential ∆9 desaturase gene was identified and successfully expressed in E. coli. A high growth temperature and not heat shock reduced transcript and protein desaturase levels in rhizobial strain. CONCLUSIONS: In B. TAL1000, the anaerobic MUFA biosynthetic pathway is supplemented by an aerobic mechanism mediated by desaturase and is down-regulated by temperature to maintain membrane fluidity under stressful conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This knowledge will be useful for developing strategies to improve a sustainable practice of this bacterium under stress and to enhance the bioprocess for the inoculants' manufacture.
Assuntos
Arachis/microbiologia , Bradyrhizobium/metabolismo , Ácidos Graxos Monoinsaturados/metabolismo , Ácidos Graxos/biossíntese , Temperatura , Aerobiose , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Bradyrhizobium/genética , Clonagem Molecular , Escherichia coli/genética , Escherichia coli/metabolismo , Ácidos Graxos Dessaturases/genética , Regulação Bacteriana da Expressão Gênica , Resposta ao Choque Térmico , Fluidez de Membrana , Dados de Sequência Molecular , NodulaçãoRESUMO
We examined and compared the activities of synthetic and hydrolytic enzymes involved in trehalose metabolism, in three peanut rhizobia strains grown in control, hypersaline, and non-ionic hyperosmotic media. Results indicated that the effects of hyperosmolarity on the synthesis and the degradation of the disaccharide were diverse. In the salt-tolerant slow-growing strain Bradyrhizobium sp. ATCC 10317, we observed increased synthesis and accumulation of trehalose under hyperosmolarity imposed by either NaCl or PEG-8000. In the other two peanut rhizobia strains, the disaccharide level did not change under hypersalinity. In the salt-sensitive slow-growing strain Bradyrhizobium sp. USDA 3187, intracellular trehalose diminished in late stationary phase-cells grown with PEG, this reduction was accompanied by both an increased activity of synthetic enzymes and a decreased activity of trehalase. In the salt-tolerant fast-growing strain Rhizobium sp. TAL 1000, we also observed a reduction of intracellular trehalose under PEG-mediated growth, this decrease was early and transiently accompanied by an enhancement of trehalase activity, afterwards, the activity of synthetic enzymes augmented.