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Mutational Analysis of the Carboxy-Terminal (YGX)4 Repeat Domain of CpsD, an Autophosphorylating Tyrosine Kinase Required for Capsule Biosynthesis in Streptococcus pneumoniae. Judy K. Morona, 2003.In Streptococcus pneumoniae, CpsB, CpsC, and CpsD are essential for encapsulation, and mutants containing deletions of cpsB, cpsC, or cpsD exhibit rough colony morphologies . CpsD is an autophosphorylating protein-tyrosine kinase, CpsC is required for CpsD tyrosine phosphorylation, and CpsB is a phosphotyrosine-protein phosphatase . We have previously shown that autophosphorylation of CpsD at tyrosine attenuates its activity and consequently reduces the level of encapsulation and negatively regulates CPS production . In this study, we further investigated the role of the carboxy-terminal (YGX)4 repeat domain of CpsD in encapsulation . A CpsD truncation mutant in which the entire (YGX)4 repeat domain was removed was indistinguishable from a strain in which the entire cpsD gene had been deleted, indicating that the carboxy-terminal (YGX)4 tail is required for CpsD activity in capsular polysaccharide production . Double mutants having a single tyrosine residue at position 2, 3, or 4 in the (YGX)4 repeat domain and lacking CpsB exhibited a rough colony morphology, indicating that in the absence of an active protein-tyrosine phosphatase, phosphorylation of just one of the tyrosine residues in the (YGX)4 repeat was sufficient to inactivate CpsD . When various mutants in which CpsD had either one or combinations of two or three tyrosine residues in the (YGX)4 repeat domain were examined, only those with three tyrosine residues in the (YGX)4 repeat domain were indistinguishable from the wild-type strain . The mutants with either one or two tyrosine residues exhibited mucoid colony morphologies . Further analysis of the mucoid strains indicated that the mucoid phenotype was not due to overproduction of capsular polysaccharide, as these strains actually produced less capsular polysaccharide than the wild-type strain . Thus, the tyrosine residues in the (YGX)4 repeat domain are essential for normal functioning of CpsD . Rapidly Increasing Prevalence of ß-Lactamase-Nonproducing, Ampicillin-Resistant Haemophilus influenzae Type b in Patients with Meningitis. Keiko Hasegawa, 2004.A total of 395 Haemophilus influenzae strains from 226 Japanese institutions participating in the Nationwide Surveillance Study Group for Bacterial Meningitis were received from 1999 to 2002 . All strains were analyzed by PCR to identify the resistance genes, and their susceptibilities to ß-lactam agents were determined . Of these strains, 29.1% were ß-lactamase nonproducing and ampicillin (AMP) susceptible (BLNAS) and lacked all resistance genes; 15.4% were ß-lactamase producing and AMP resistant and had the blaTEM-1 gene; 30.6% were ß-lactamase nonproducing and AMP resistant (low-BLNAR) and had a Lys-526 or His-517 amino acid substitution in ftsI encoding PBP 3; 13.9% were ß-lactamase nonproducing and AMP resistant (BLNAR) and had an additional substitution of Thr-385 in ftsI; 9.1% were amoxicillin-clavulanic acid resistant (BLPACR I) and had the blaTEM-1 gene and a Lys-526 or His-517 amino acid substitution in ftsI; and 1.8% showed resistance similar to that of the BLPACR I group (BLPACR II) but had blaTEM-1 gene and ftsI substitutions, as was the case for the BLNAR strains . All but three strains were serotype b . The prevalence of BLNAR strains has increased rapidly: 0% in 1999, 5.8% in 2000, 14.1% in 2001, and 21.3% in 2002 . The MICs at which 90% of BLNAR isolates were inhibited were as follows: AMP, 16 µg/ml; cefotaxime, 1 µg/ml; ceftriaxone, 0.25 µg/ml; and meropenem, 0.5 µg/ml . All of these values were higher than those for the BLNAS counterpart strains . The relatively wide distributions of the ß-lactam MICs for BLNAR strains presumably reflect variations in ftsI gene mutations . Pulsed-field gel electrophoresis suggested the rapid spread of specific H . influenzae type b strains throughout Japan . Expedited vaccination, rapid identification, and judicious antibiotic use could slow their spread . Cyanobacterial Protease Inhibitor Microviridin J Causes a Lethal Molting Disruption in Daphnia pulicaria. Thomas Rohrlack, 2004. Chromosomal Locus That Affects Pathogenicity of Rhodococcus fascians. Danny Vereecke, 2002.The gram-positive plant pathogen Rhodococcus fascians provokes leafy gall formation on a wide range of plants through secretion of signal molecules that interfere with the hormone balance of the host . Crucial virulence genes are located on a linear plasmid, and their expression is tightly controlled . A mutant with a mutation in a chromosomal locus that affected virulence was isolated . The mutation was located in gene vicA, which encodes a malate synthase and is functional in the glyoxylate shunt of the Krebs cycle . VicA is required for efficient in planta growth in symptomatic, but not in normal, plant tissue, indicating that the metabolic requirement of the bacteria or the nutritional environment in plants or both change during the interaction . We propose that induced hyperplasia on plants represents specific niches for the causative organisms as a result of physiological alterations in the symptomatic tissue . Hence, such interaction could be referred to as metabolic habitat modification .
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