Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Bayer, Manfred E.

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During his career, David Baltimore has served on

numerous governmental advisory committees. Apart from

being a member of the National Academy of Sciences, he is

also affiliated with the Pontifical Academy of Sciences, the

American Academy of Arts and Sciences, and the Royal

Society of London. At the end of 1996 he was appointed head

of the newly created AIDS Vaccine Research Committee of

the National Institutes of Health, a group that supports all

efforts to accelerate the discovery of a vaccine against AIDS.

See alsoAIDS, recent advances in research and treatment;

Immunogenetics; Viral genetics; Viral vectors in gene therapy;

Viruses and responses to viral infection

BBasidomycetesASIDOMYCETES

Basidomycetes are a fungal group belonging to the Eukarya

domain, which includes all life forms composed by nucleated

cells. Basidomycetes are classified under the Fungikingdom

as belonging to the phylum –mycota (i.e., Basidomycota or

Basidiomycota), class –mycetes (i.e., Basidomycetes). Fungi

are frequently parasitesthat decompose organic material from

their hosts, such as those growing on rotten wood, although

some may cause serious plant diseases such as smuts

(Ustomycetes) and rusts (Teliomycetes). Some live in a sym-

biotic relationship with plant roots (Mycorrhizae). A cell type

termed basidium is responsible for sexual spore formation in

Basidomycetes, through nuclear fusion followed by meiosis,

thus forming haploid basidiospores. Fungi pertaining to the

Basidomycota phylum may present dikaryotic hyphae, i.e.,

walled filamentous cylindrical structures resembling branches

that are formed when the two nuclei in the apical cell of a

hypha divide simultaneously. One divides in the hyphal main

axis and the other into the clamp, thus giving origin to a tem-

porary monokaryotic clamp cell that is then fused to the sub

apical cell, restoring the dikaryotic status. Spores are lined

next to one another on the several neighboring basidia that

form the Hymenium on the mushroom gill. Each spore usually

bears the haploid product of meiosis. In adverse conditions,

the spores may remain dormant for long periods, from months

to years. When conditions are favorable, the spores germinate

into uninucleated hyphae, forming monokaryotic mycelia. A

dikaryotic myceliumis formed as the result of the fusion of

two monokaryotic mycelia. Basidomycetes’ sexual spores are

more often than not disseminated through the wind, either by

passive or forced spore discharge.

Basidomycetes comprises over 15,000 species, belong-

ing to 15 different orders, most of them wood-rotting species.

Some examples of Basidomycetes are as follows: Coral

Fungus or Ramaria, pertaining to the Hymeniales order;

Stinkhorn or Phallus, from the Phallales order; Corn smut or

Ustilago, from the Ustilaginales order; Puffball or

Lycoperdon, from the Lycoperdales order; White Button Pizza

or Agaricus bisporus,from the Agaricales order.

The cell walls of fungi contain distinct layers, mainly

constituted by chitinand not by cellulose. Multicellular fungi

such as mushrooms have their vegetative bodies constituted

mainly by filamentous hyphae. As parasites, Basidomycota

and other fungi phyla (i.e., Chytridiomycota, Zygomycota,

Ascomycota), do not itlize photosynthesis, and therefore, lack

clorophyll. They produce instead several different exoen-

zymes, which are released directly on their hosts through

invading filaments that can reach the target substance to be

enzymatically decomposed. The exoenzymes are utilized in

the digestion of the available organic substance from which

they absorb micronutrients to synthesize and store great

amounts of glycogen, whereas plants store energy under the

form of starch. They also contain in their cell membranes

ergosterol, a sterol found exclusively in fungi.

See alsoChitin; Eukaryotes; Fungal genetics; Mycology

BATCH AND CONTINUOUS CULTURE •see

LABORATORY TECHNIQUES IN MICROBIOLOGY

BBayer, Manfred E.AYER, MANFREDE.(1928- )

German physician

While educated as a physician, Manfred Bayer is best known

for the series of fundamental contributions he has made to the

study of bacterial and viral ultrastructure. He was the first per-

son to visualize the yellow fevervirus in cultured cells, and to

obtain ultrathin sections of the changes caused to the cell wall

of Escherichia coliby the antibiotic penicillin. The latter

achievement helped guide the development of future antibi-

oticsactive against the bacterial wall. In the 1960s, he identi-

fied zones of adhesion between the inner and outer

membranes of Escherichia coli. Bayer’s rigorous experiments

established that these adhesion zones that were apparent in

thin sections of cells examined by the technique of transmis-

sion electron microscopy had biochemical significance e.g.,

routing of bacterial components to the surface of the cell, route

for passage of virusesinto the bacterium, specific site of cer-

tain enzyme activity). In recognition of his efforts, the adhe-

sion sites were dubbed “Bayer’s adhesion zones.”

Bayer was born in Görlitz, Prussia (now Poland).

Following his high school education he enrolled in the biol-

ogy program at the University of Kiel in Germany. He

obtained his degree in 1949. Following this, he was accepted

for medical studies at the University of Hamburg, Germany.

He completed his preclinical training in 1953 and clinical

training in 1955. From 1957 to 1959 he studied physics at the

same university. During this same period he earned his

accreditation as a physician, and undertook research studies

in pathology. This research led to a Research Associate posi-

tion at the University of Hamburg from 1957 to 1961. Also

during this period Bayer undertook diploma studies at the

university’s Institute of Tropical Medicine and Parasitology.

He received his diploma in 1961.

From 1960 to 1962, Bayer was an Assistant Member of

the Institute of Tropical Diseases and Parasitology. Then, he

immigrated to the United States to take up the position of

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