In the representative gut bacterium Lactobacillus plantarum, we identified genes encoding the enzymes involved in a saturation metabolism of polyunsaturated fatty acids and revealed in detail the metabolic pathway that generates hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and partially saturated transfatty acids as intermediates. Furthermore, we observed these intermediates, especially hydroxy fatty acids, in host organs. Levels of hydroxy fatty acids were much higher in specific pathogen-free mice than in germ-free mice, indicating that these fatty acids are generated through polyunsaturated fatty acids metabolism of gastrointestinal microorganisms. These findings suggested that lipid metabolism by gastrointestinal microbes affects the health of the host by modifying fatty acid composition.biohydrogenation | hydratase | fatty acid isomerase | conjugated linoleic acid | lipid nutrition

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A strain of Streptomyces lividans, TK24, was found to produce a pigmented antibiotic, actinorhodin, although S. lividans normally does not produce this antibiotic. Genetic analyses revealed that a streptomycin-resistant mutation str-6 in strain TK24 is responsible for induction of antibiotic synthesis. DNA sequencing showed that str-6 is a point mutation in the rpsL gene encoding ribosomal protein S12, changing Lys-88 to Glu. Gene replacement experiments with the Lys883Glu str allele demonstrated unambiguously that the str mutation is alone responsible for the activation of actinorhodin production observed. In contrast, the strA1 mutation, a genetic marker frequently used for crosses, did not restore actinorhodin production and was found to result in an amino acid alteration of Lys-43 to Asn. Induction of actinorhodin production was also detected in strain TK21, which does not harbor the str-6 mutation, when cells were incubated with sufficient streptomycin or tetracycline to reduce the cell's growth rate, and 40 and 3% of streptomycin-or tetracycline-resistant mutants, respectively, derived from strain TK21 produced actinorhodin. Streptomycin-resistant mutations also blocked the inhibitory effects of relA and brgA mutations on antibiotic production, aerial mycelium formation or both. These str mutations changed Lys-88 to Glu or Arg and Arg-86 to His in ribosomal protein S12. The decrease in streptomycin production in relC mutants in Streptomyces griseus could also be abolished completely by introducing streptomycin-resistant mutations, although the impairment in antibiotic production due to bldA (in Streptomyces coelicolor) or afs mutations (in S. griseus) was not eliminated. These results indicate that the onset and extent of secondary metabolism in Streptomyces spp. is significantly controlled by the translational machinery.

Mon1 and Ccz1 were identified from a gene deletion library as mutants defective in the vacuolar import of aminopeptidase I (Ape1) via the cytoplasm to vacuole targeting (Cvt) pathway. The mon1⌬ and ccz1⌬ strains also displayed defects in autophagy and pexophagy, degradative pathways that share protein machinery and mechanistic features with the biosynthetic Cvt pathway. Further analyses indicated that Mon1, like Ccz1, was required in nearly all membrane-trafficking pathways where the vacuole represented the terminal acceptor compartment. Accordingly, both deletion strains had kinetic defects in the biosynthetic delivery of resident vacuolar hydrolases through the CPY, ALP, and MVB pathways. Biochemical and microscopy studies suggested that Mon1 and Ccz1 functioned after transport vesicle formation but before (or at) the fusion step with the vacuole. Thus, ccz1⌬ and mon1⌬ are the Compartmentalization allows eukaryotic cells to regulate intracellular functions by separating competing reactions and localizing enzymes and substrates at specific locations within the cell. Efficient compartmentalization necessitates dynamic protein trafficking processes by which cells are able to establish and maintain the identity and function of each organelle. The vacuole (lysosome) of the yeast Saccharomyces cerevisiae plays a central role in the turnover of cytoplasmic organelles, degradation of intracellular/extracellular components, and maintenance of cellular physiology (1). To carry out these functions, the vacuole maintains a variety of degradative enzymes. Both resident hydrolases and their substrates arrive at this destination through a variety of sorting pathways. The main routes by which vacuolar hydrolases are delivered to this organelle are the carboxypeptidase Y (CPY), 1 alkaline phosphatase (ALP), and multivesicular body (MVB) pathways, which involve transit through a portion of the secretory pathway, and the cytoplasm to vacuole targeting (Cvt) pathway by which the cargo molecules are packaged as cytosolic membrane-bound intermediates (2, 3). Resident proteins are also transmitted by inheritance from mother cell vacuoles to daughter cells during cell division (4). Substrates enter the vacuole through endocytosis, autophagy and the vacuole import and degradation pathway (reviewed in Ref. 5). One common feature in all of these processes is membrane fusion. The membrane fusion mechanism acts to ensure specificity for the directed movement of proteins while also maintaining the distinct composition of each organelle within the highly compartmentalized eukaryotic cell.The cytoplasm to vacuole targeting pathway that is used to deliver the soluble hydrolase aminopeptidase I (Ape1) to the vacuole has been under investigation (for reviews see Refs. 2, 5, and 6). Under vegetative conditions, precursor Ape1 (prApe1) is assembled into a large Cvt complex composed in part of multiple prApe1 dodecamers in the cytosol that becomes enwrapped within a double-membrane Cvt vesicle (7). Upon completion, the cytosolic Cvt vesicle target...

Yeasts used in bread making are exposed to high concentrations of sucrose during sweet dough fermentation. Despite its importance, tolerance to high-sucrose stress is poorly understood at the gene level. To clarify the genes required for tolerance to high-sucrose stress, genome-wide screening was undertaken using the complete deletion strain collection of diploid Saccharomyces cerevisiae. The screening identified 273 deletions that yielded high sucrose sensitivity, approximately 20 of which were previously uncharacterized. These 273 deleted genes were classified based on their cellular function and localization of their gene products. Cross-sensitivity of the high-sucrose-sensitive mutants to high concentrations of NaCl and sorbitol was studied. Among the 273 sucrose-sensitive deletion mutants, 269 showed cross-sensitivities to sorbitol or NaCl, and four (i.e. ade5,7, ade6, ade8, and pde2) were specifically sensitive to high sucrose. The general stress response pathways via high-osmolarity glycerol and stress response element pathways and the function of the invertase in the ade mutants were similar to those in the wild-type strain. In the presence of high-sucrose stress, intracellular contents of ATP in ade mutants were at least twofold lower than that of the wild-type cells, suggesting that depletion of ATP is a factor in sensitivity to high-sucrose stress. The genes identified in this study might be important for tolerance to high-sucrose stress, and therefore should be target genes in future research into molecular modification for breeding of yeast tolerant to high-sucrose stress.