106 research outputs found
Ancient origin of the biosynthesis of lignin precursors
BACKGROUND: Lignin plays an important role in plant structural support and water transport, and is considered one of the hallmarks of land plants. The recent discovery of lignin or its precursors in various algae has raised questions on the evolution of its biosynthetic pathway, which could be much more ancient than previously thought. To determine the taxonomic distribution of the lignin biosynthesis genes, we screened all publicly available genomes of algae and their closest non-photosynthetic relatives, as well as representative land plants. We also performed phylogenetic analysis of these genes to decipher the evolution and origin(s) of lignin biosynthesis. RESULTS: Enzymes involved in making p-coumaryl alcohol, the simplest lignin monomer, are found in a variety of photosynthetic eukaryotes, including diatoms, dinoflagellates, haptophytes, cryptophytes as well as green and red algae. Phylogenetic analysis of these enzymes suggests that they are ancient and spread to some secondarily photosynthetic lineages when they acquired red and/or green algal endosymbionts. In some cases, one or more of these enzymes was likely acquired through lateral gene transfer (LGT) from bacteria. CONCLUSIONS: Genes associated with p-coumaryl alcohol biosynthesis are likely to have evolved long before the transition of photosynthetic eukaryotes to land. The original function of this lignin precursor is therefore unlikely to have been related to water transport. We suggest that it participates in the biological defense of some unicellular and multicellular algae. REVIEWERS: This article was reviewed by Mark Ragan, Uri Gophna, Philippe Deschamps
Acute and subchronic exposure to air particulate matter induces expression of angiotensin and bradykinin-related genes in the lungs and heart: Angiotensin-II type-I receptor as a molecular target of particulate matter exposure
STUDIES ON ANTIBIOTIC SYNERGISM AND ANTAGONISM : Synergism among Seven Antibiotics against Various Bacteria in vitro
In an increasing nuimber of microbial infections of man, treatment with single antibiotics fails to cure. Some of these infections, however, respond favorably to combined treatment with two antibiotic drugs. Certain pairs of these drugs have proved successful in a limited number of clinical situations. An outstand-ing example is the frequent cure of bacterial endocarditis due to enterococci by the simultaneous administration of penicillin and streptomycin, whereas neither of these drugs alone cures more than a small number of cases (Hunter, 1950; Robbins and Tompsett, 1951; Cates, Christie, and Garrod, 1951). The synergism of penicillin and streptomycin in vitro is manifested by a marked in-crease in the bactericidal rate beyond that obtainable with any concentration of either drug alone and also by the killing of the entire exposed bacterial popu-lation, a feat which neither of the two drugs can achieve alone (Jawetz, Guinnison, and Coleman, 1950; Gunnison, Jawetz, and Coleman, 1950). As more microorganisms which are resistant to certain antibiotics are encoun-tered in medical practice, there is an increased temptation to employ more than one antimicrobial drug routinely. Such indiscriminate use of two drugs is probably inadvisable inasmuch as antagonism between certain antibiotics has been dem-onstrated both in vitro and in experimental animals (Jawetz, Gunnison, Speck, and Coleman, 1951; Speck, Jawetz, and Gunnison, 1951; Jawetz, Gunnison, and Speck, 1951). To obtain a rational basis for the selection of antibiotics for com-bined therapy it is essential that the relationships among these drugs be studied. This report deals with some quantitative relationships in several synergistic combinations of antibiotics active against a number of different bacteria. The results may contribute clues to the mechanism of combined antibiotic action. An attempt has been made to answer some of the questions which arise as to the combined effect of two antibiotics in vitro
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