Two types of Pseudomonas putida PpG2 mutants which were unable to degrade branched-chain amino acids were isolated after mutagenesis and selection for ability to grow on succinate, but not valine, as a sole source of carbon. These isolates were characterized by growth on the three branched-chain amino acids (valine, isoleucine, and leucine), on the corresponding branched-chain keto acids (2-ketoisovalerate, 2-keto-3-methylvalerate, and 2-ketoisocaproate), and on other selected intermediates as carbon sources, and by their enzymatic composition. One group of mutants lost 2-ketoisovalerate-inducible branched-chain keto acid dehydrogenase that was active on all three keto acids. There was also a concomitant loss of ability to grow on all three branched-chain amino acids as well as on all three corresponding keto acids, but there was retention of ability to use subsequent intermediates in the catabolism of branched-chain amino acids. Another type of mutant showed a marked reduction in branched-chain amino acid transaminase activity and grew poorly at the expense of all three amino acids, but it utilized subsequent intermediates as carbon sources. Both the transaminase and branched-chain keto acid dehydrogenase mutants retained the ability to degrade camphor. These findings are consistent with the view that branched-chain amino acid transaminase and branched-chain keto acid dehydrogenase are common enzymes in the catabolism of valine, isoleucine, and leucine.

Alcohol Oxidoreductases↗

PubMed1973

Ultrastructural changes in hamster tracheal ring cultures exposed to Mycoplasma pneumoniae.

Ultrastructural studies of lung biopsies in this laboratory from 2 children with chronic respiratory disease and elevated titers to Mycoplasma pneumoniae showed increased pleomorphic lysosomes in alveolar macrophages. This suggested that intracellular digestion might be an important feature of mycoplasma infection and an in vitro study was undertaken. Tracheal ring cultures from 35 Syrian hamsters were exposed to Clyde M129 strain of M pneumoniae. Controls consisted of untreated tracheal rings from the same animals. Both groups were subjected to light, fluorescent, and electron microscopy. Cultures exposed to virulent mycoplasma exhibited specific immunofluorescence at mucosal surfaces and in the submucosa. Mucosal cytopathic changes and submucosal necrosis were prominent. Submucosal macrophages contained increased numbers of lysosomes, some of which contained mycoplasma-like forms. If Mycoplasma pneumoniae are ingested by macrophages, this would provide a mechanism through which immune phenomena could occur and would partially explain the prominent peribronchial lymphocytic accumulation of human mycoplasma infection.

Animals↗

PubMed1971