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Melanins are found universally in nature and are implicated in the pathogenesis of several important human fungal pathogens. This study investigated whether the conidia and the yeast cells of the thermally dimorphic fungal pathogen Penicillium marneffei produce melanin or melanin-like compounds in vitro and during infection. Treatment of conidia with proteolytic enzymes, denaturant and concentrated hot acid yielded dark particles that were similar in size and shape to the conidia. A melanin-binding monoclonal antibody (mAb) labelled pigmented conidia, yeast cells and the isolated particles as determined by i mmunofluorescence microscopy. Electron spin resonance spectroscopy revealed that particles derived from pigmented conidia contained a stable free radical compound, consistent with their identification as melanins. Skin tissue from penicilliosis marneffei patients contained yeast cells that were labelled by melanin-binding mAb. Additionally, sera from P. marneffei-infected mice developed a significant antibody response (both IgG and IgM) against melanin. Phenoloxidase activity capable of synthesizing melanin from L-DOPA was detected in cytoplasmic yeast cell extracts. These findings indicate that P. marneffei conidia and yeast cells can produce melanin or melanin-like compounds in vitro and that the yeast cells can synthesize pigment in vivo. Accordingly this pigment may play some role in the virulence of P. marneffei. Abbreviations: DHN, dihydroxynaphthalene; DOPA, 3,4-dihydroxyphenylalanine; ESR, electron spin resonance spectroscopy; SEM, scanning electron microscopy; TEM, transmission electron microscopy.

Research was conducted to examine the serotype 14 variants of the Spanish penicillin-resistant serotype 9V clone of Streptococcus pneumoniae which have resulted from large recombinational replacements of the cpsA-pbp1a region. The relationship of the penicillin-resistant serotype 14 isolates to other penicillin-resistant pneumococci was established via multilocus sequence typing and were demonstrated to be serotype variants of the MPSp9V. The molecular basis of the emergence of the variants was elucidated through an analysis of their capsular locus and flanking regions.

Glucose was utilized as a growth-limiting component for a high-penicillin-yielding strain of Penicillium chrysogenum grown in a chemically defined medium. In this study, the high production of penicillin was sustained by maintaining a high amount of phenoxyacetic acid concentration in the strain. This also reduced the loss of the pathway intermediate isopenicillin N in the extracellular medium.

Previous research has divided Penicillium roqueforti into two varieties, P. roqueforti var. roqueforti, which is used for cheese starter cultures, and P. roqueforti var. carneum, which produces patulin. However, a sequence analysis of Penicillium isolates shows the existence of another variety of P. roqueforti, P. paneum. Random Amplified Polymorphic DNA fingerprinting confirms the existence of the variety.

Western blotting and immunoprecipitation analyses help characterize the penicillin-binding proteins (PBPs) of Shigella dysenteriae. A comparative study reveals the close similarity between the PBP type of the membranes of S. dysenteriae and that of Escherichia coli membranes. Standard procedures facilitate the purification of a 38 kDa PBP, an important target for the oxacephem moxalactam, the penem SCH34343 and the cephamycin cefoxitin. Stationary-phase cells of S. dysenteriae have significant levels of PBP.

Beta-lactam derivatives such as benzylpenicillin inhibit bacterial division because they slow down the rate of peptidoglycan synthesis. Peptidoglycan is a necessary element in the formation of the FtsZ ring,a component of the cellular septum that determines the final size of the mature cell. Penicillin-binding protein is formed after the FtsZ ring is formed and its blocking by penicillin leads to filament-shaped instead of normal cells. In addition, the inhibitory effects of penicillin varies in different nutritional environments.