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L Chamberlin

Publications and source records attributed to L Chamberlin.

7 recordsLinked to original sources
PubMed1999

Evidence that the extracytoplasmic function sigma factor sigmaE is required for normal cell wall structure in Streptomyces coelicolor A3(2).

The sigE gene of Streptomyces coelicolor A3(2) encodes an RNA polymerase sigma factor belonging to the extracytoplasmic function (ECF) subfamily. Constructed sigE deletion and disruption mutants were more sensitive than the parent to muramidases such as hen egg white lysozyme and to the CwlA amidase from Bacillus subtilis. This correlated with an altered muropeptide profile, as determined by reverse-phase high-performance liquid chromatography analysis of lytic digests of purified peptidoglycan. The sigE mutants required high levels of magnesium for normal growth and sporulation, overproducing the antibiotic actinorhodin and forming crenellated colonies in its absence. Together, these data suggest that sigE is required for normal cell wall structure. The role of sigmaE was further investigated by analyzing the expression of hrdD, which is partially sigE dependent. The hrdD gene, which encodes the sigmaHrdD subunit of RNA polymerase, is transcribed from two promoters, hrdDp1 and hrdDp2, both similar to promoters recognized by other ECF sigma factors. The activities of hrdDp1 and hrdDp2 were reduced 20- and 3-fold, respectively, in sigE mutants, although only hrdDp1 was recognized by EsigmaE in vitro. Growth on media deficient in magnesium caused the induction of both hrdD promoters in a sigE-dependent manner.

Amidohydrolases↗
PubMed1998

Developmental regulation of transcription of whiE, a locus specifying the polyketide spore pigment in Streptomyces coelicolor A3 (2)

whiE is a complex locus that specifies the polyketide spore pigment in Streptomyces coelicolor A3(2). Two divergently oriented promoters, whiEP1 and whiEP2, were identified in the whiE gene cluster, and their activities were analyzed during colony development in wild-type and sporulation-deficient strains. Both promoters were developmentally regulated; whiEP1 and whiEP2 transcripts were detected transiently at approximately the time when sporulation septa were observed in the aerial hyphae, and transcription from both promoters depended on each of the six known "early" whi genes required for sporulation septum formation (whiA, -B, -G, -H, -I, and -J). Mutation of the late sporulation-specific sigma factor gene, sigF, had no effect on the activity of whiEP1 but blocked transcription from whiEP2. However, sigmaF-containing holoenzyme was not sufficient to direct transcription of whiEP2 in vitro. The whiEP2 promoter controls expression of whiE ORFVIII, encoding a putative flavin adenine dinucleotide-dependent hydroxylase that catalyzes a late tailoring step in the spore pigment biosynthetic pathway. Disruption of whiE ORFVIII causes a change in spore color, from grey to greenish (T.-W. Yu and D. A. Hopwood, Microbiology 141:2779-2791, 1995). Consistent with these observations, construction of a sigF null mutant of S. coelicolor M145 caused the same change in spore color, showing that disruption of sigF in S. coelicolor changes the nature of the spore pigment rather than preventing its synthesis altogether.

Bacterial Proteins↗
PubMed1997

Sigma-E is required for the production of the antibiotic actinomycin in Streptomyces antibioticus.

The phsA gene encodes phenoxazinone synthase (PHS), which catalyses the penultimate step in the pathway for actinomycin biosynthesis in Streptomyces antibioticus. The phsA promoter strikingly resembles a putative Streptomyces sigma E cognate promoter, and purified E sigma E holoenzyme transcribed the phsA promoter in vitro. However, the phsA promoter was still active in an S. antibioticus sigE null mutant and the level of PHS activity was unaffected. Despite this, disruption of sigE blocked actinomycin production completely. The loss of actinomycin production correlated with a 10-fold decrease in the activity of actinomycin synthetase I, the enzyme which catalyses the activation of the precursor of the actinomycin chromophore.

Amino Acid Sequence↗
PubMed1992

Functional and serological analysis of type II immunoglobulin G-binding proteins expressed by pathogenic group A streptococci.

Bacterial immunoglobulin-binding proteins expressed on the surface of group A streptococci represent a heterogeneous family of functionally related proteins. In this report, we describe efficient methods for extracting immunoglobulin-binding proteins and classifying them functionally and antigenically. A common characteristic of immunoglobulin-binding proteins expressed by group A streptococci appears to be the absence of internal methionine residues in the binding protein. This has enabled development of a rapid, efficient, cyanogen bromide-based extraction procedure for solubilizing these molecules from intact bacteria. Studies carried out with a series of monospecific polyclonal antibodies prepared in chickens have identified two major antigenic classes of immunoglobulin-binding proteins. The methods described in this report facilitate a rapid functional and serological screening of immunoglobulin-binding proteins that should now enable detailed epidemiological studies of the importance of these molecules in group A streptococcal infections and their relationship to other surface proteins, in particular, the antiphagocytic M protein.

Antigens, Bacterial↗
PubMed1990

Heavy contamination of operating room air by Penicillium species: identification of the source and attempts at decontamination.

Increased rates of nosocomial infection caused by filamentous fungi in immunocompromised patients prompted microbiologic surveillance of the central air handling systems in our hospital. During a 4-year period, Penicillium species were isolated from 47 patients, including two with surgical wound infections caused by Penicillium. Counts of Penicillium in operating room air were much higher (195 colony-forming units [CFU]/m3) than in 95% filtered corridor air (14.6 CFU/m3; p less than 0.01). Ventilation ducts and terminal units lined with fiberglass in the operating room air handling system were heavily contaminated by Penicillium; the fiberglass was also contaminated with Aspergillus species. Corrective measures included filter replacement and decontamination of the ventilation system with aerosolized chlorine solution. Although operating room air remained free of filamentous fungi during the next 7 months, contamination eventually recurred and required repeated decontamination. We believe that certification guidelines are highly desirable for hospital ventilation systems, especially if the system serves immunocompromised patients.

Air Microbiology↗