ABSTRACT
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.
Subject(s)
Arachis/microbiology , Bradyrhizobium/metabolism , Rhizobium/metabolism , Trehalase/metabolism , Trehalose/metabolism , Bradyrhizobium/enzymology , Culture Media , Hydrolysis , Osmolar Concentration , Rhizobium/enzymologyABSTRACT
Rhizobium meliloti 300hl3 reached the stationary phase of growth very quickly and had an early death when 8.6 muM parathion was added to the growth medium at the start of the culture. Cells also changed their quantitative composition: total carbohydrate content and poly-beta-hydroxybutyrate accumulation diminished, proteins and phospholipids of cellular membranes increased, and some alterations in the proportion of membrane fatty acids were noticed.
Subject(s)
Bacterial Proteins/metabolism , Lipid Metabolism , Lipopolysaccharides/metabolism , Parathion/pharmacology , Rhizobium/growth & development , Kinetics , Lipoproteins/metabolism , Rhizobium/drug effects , Rhizobium/metabolismABSTRACT
A plasmid-containing wild-type Escherichia coli strain was treated with two plasmid-curing agents, sodium dodecyl sulfate and ethidium bromide. Plasmid elimination was accompanied by drastic changes in the morphology of the colonies. Analysis of the cured strain by scanning and transmission electron microscopy showed important alterations in size and morphology of the cells. Metabolic differences were also found between the wild-type and cured cells.
Subject(s)
Escherichia coli/genetics , Plasmids , Cell Membrane/ultrastructure , Chloramphenicol/pharmacology , Drug Resistance, Microbial , Escherichia coli/drug effects , Escherichia coli/ultrastructure , Microscopy, ElectronABSTRACT
Cells of Escherichia coli contained an altered phospholipid and fatty acid composition when grown in the presence of some pesticides. Whereas parathion increased the concentration of all phospholipid species without changes in their polar head groups. DDT (dichlorodiphenyltrichloroethane) decreased the proportion of neutral serine-derived phosphatides and dieldrin decreased the proportion of negatively charged phospholipids. The saturated/unsaturated plus cyclopropane fatty acid ratio was increased in all cases. The changes suggested that cells adapted their membrane lipids to compensate for the presence of pesticides in the environment.
