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Slr1293 in Synechocystis sp . Strain PCC 6803 Is the C-3',4' Desaturase (CrtD) Involved in Myxoxanthophyll Biosynthesis. Hatem E. Mohamed, 2004.When grown at high light intensity, more than a quarter of the total carotenoids in the unicellular cyanobacterium Synechocystis consists of myxoxanthophyll, a polar carotenoid glycoside . The biosynthetic pathway of myxoxanthophyll is unknown but is presumed to involve a number of enzymes, including a C-3',4' desaturase required to add one double bond to generate 11 conjugated double bonds in the monocyclic myxoxanthophyll . A candidate for this desaturase is Slr1293, which was identified by genome similarity searching . To determine whether Slr1293 is a desaturase recognizing neurosporene and lycopene, slr1293 was expressed in Escherichia coli strains accumulating neurosporene or lycopene . Confirming such a desaturase function for Slr1293, these E . coli strains accumulated 3',4'-didehydroneurosporene and 3',4'-didehydrolycopene, respectively . Indeed, deletion of slr1293 in Synechocystis provides further evidence that Slr1293 is a desaturase recognizing neurosporene: In the slr1293 deletion mutant, neurosporene was found to accumulate and was further processed to produce neurosporene glycoside . Neurosporene hereby becomes a primary candidate to be the branch point molecule between carotene and myxoxanthophyll biosynthesis in this cyanobacterium . The slr1293 gene was concluded to encode a C-3',4' desaturase that is essential for myxoxanthophyll biosynthesis, and thus it was designated as crtD . Furthermore, as Slr1293 appears to recognize neurosporene and to catalyze the first committed step on the myxoxanthophyll biosynthesis pathway, Slr1293 plays a pivotal role in directing a portion of the precursor pool for carotenoid biosynthesis toward myxoxanthophyll biosynthesis in Synechocystis sp . strain PCC 6803 . In Vitro Pharmacodynamic Characteristics of Amphotericin B, Caspofungin, Fluconazole, and Voriconazole against Bloodstream Isolates of Infrequent Candida Species from Patients with Hematologic Malignancies. Giovanni Di Bonaventura, 2004.Time-kill and postantifungal effect (PAFE) of amphotericin B, caspofungin, fluconazole, and voriconazole were determined against clinical isolates of Candida guilliermondii, Candida kefyr, and Candida lusitaniae . Azoles displayed fungistatic activity and no measurable PAFE, regardless of the concentration tested . Amphotericin B and caspofungin demonstrated concentration-dependent fungicidal activity, although amphotericin B only produced a significant dose-dependent PAFE against all isolates tested . Role of Menaquinones in Fe(III) Reduction by Membrane Fractions of Shewanella putrefaciens. Daad A. Saffarini, 2002.Two Tn5-generated mutants of Shewanella putrefaciens with insertions in menD and menB were isolated and analyzed . Both mutants were deficient in the use of several terminal electron acceptors, including Fe(III) . This deficiency was overcome by the addition of menaquinone (vitamin K2) . Isolated membrane fractions from both mutants were unable to reduce Fe(III) in the absence of added menaquinone when formate was used as the electron donor . These results indicate that menaquinones are essential components for the reduction of Fe(III) by both whole cells and purified membrane fractions when formate or lactate is used as the electron donor . Rod Shape Determination by the Bacillus subtilis Class B Penicillin-Binding Proteins Encoded by pbpA and pbpH. Yuping Wei, 2003.The peptidoglycan cell wall determines the shape and structural integrity of a bacterial cell . Class B penicillin-binding proteins (PBPs) carry a transpeptidase activity that cross-links peptidoglycan strands via their peptide side chains, and some of these proteins are directly involved in cell shape determination . No Bacillus subtilis PBP with a clear role in rod shape maintenance has been identified . However, previous studies showed that during outgrowth of pbpA mutant spores, the cells grew in an ovoid shape for several hours before they recovered and took on a normal rod shape . It was postulated that another PBP, expressed later during outgrowth, was able to compensate for the lack of the pbpA product, PBP2a, and to guide the formation of a rod shape . The B . subtilis pbpH (ykuA) gene product is predicted to be a class B PBP with greatest sequence similarity to PBP2a . We found that a pbpH-lacZ fusion was expressed at very low levels in early log phase and increased in late log phase . A pbpH null mutant was indistinguishable from the wild-type, but a pbpA pbpH double mutant was nonviable . When pbpH was placed under the control of an inducible promoter in a pbpA mutant, viability was dependent on pbpH expression . Growth of this strain in the absence of inducer resulted in conversion of the cells from rods to ovoid/round shapes and lysis . We conclude that PBP2a and PbpH play redundant roles in formation of a rod-shaped peptidoglycan cell wall . The Absence of FtsH Metalloprotease Activity Causes Overexpression of the  W-Controlled pbpE Gene, Resulting in Filamentous Growth of Bacillus subtilis.Stephan Zellmeier, 2003.FtsH is a membrane-bound and energy-dependent metalloprotease in bacteria which is involved in the posttranslational control of the activity of a variety of important transcription factors and in the degradation of uncomplexed integral membrane proteins . For Bacillus subtilis, little is known about the target proteins of FtsH protease . Its gene is not essential, but knockout strains display a pleiotropic phenotype including sensitivity toward salt and heat stress, defects in sporulation and competence, and largely filamentous growth . Comparison of the intracellular proteomes of wild-type and ftsH knockout strains revealed that at least nine proteins accumulated in the absence of ftsH, four of which could be identified . Two of these proteins turned out to be members of the W regulon . Accumulation of one of these
W-controlled proteins, the penicillin-binding protein PBP4*, was analyzed in more detail . We could show that PBP4* is not a proteolytic substrate of FtsH and that its overproduction is due to the enhanced transcription of its gene (pbpE) in ftsH null mutants . The filamentous growth phenotype of
 ftsH strains was abolished in a
ftsH
pbpE double knockout . In ftsH wild-type strains with the pbpE gene under regulatable control, pbpE overexpression caused filamentation of the cells . DNA macroarray analysis revealed that most genes of the
W regulon are transcribed at elevated levels in an ftsH mutant . The influence of FtsH on
W-controlled genes is discussed .
Alkylphenol Biotransformations Catalyzed by 4-Ethylphenol Methylenehydroxylase. David J. Hopper, 2003.4-Ethylphenol methylenehydroxylase from Pseudomonas putida JD1 acts by dehydrogenation of its substrate to give a quinone methide, which is then hydrated to an alcohol . It was shown to be active with a range of 4-alkylphenols as substrates . 4-n-Propylphenol, 4-n-butylphenol, chavicol, and 4-hydroxydiphenylmethane were hydroxylated on the methylene group next to the benzene ring and produced the corresponding chiral alcohol as the major product . The alcohols 1-(4'-hydroxyphenyl)propanol and 1-(4'-hydroxyphenyl)-2-propen-1-ol, produced by the biotransformation of 4-n-propylphenol and chavicol, respectively, were shown to be R(+) enantiomers . 5-Indanol, 6-hydroxytetralin, 4-isopropylphenol, and cyclohexylphenol, with cyclic or branched alkyl groups, gave the corresponding vinyl compounds as their major products .
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