Environmental Microbiology of Aquatic and Waste Systems

4.1 Taxonomy of Microorganisms in Aquatic Environments 101

7 MICROVIRIDAE

Structure
Non­enveloped, round, icosahedral symmetry (T=1), about 30
nm in diameter. The capsid consists of 12 pentagonal trumpet-
shaped pentomers. The virion is composed of 60 copies each of
the F, G, and J proteins, and 12 copies of the H protein. There are
12 spikes which are each composed of 5 G and one H proteins.

Host

Attacks Bdellovibrio, Chlamydia, Enterobacteria, Spiroplasma,

Enterobacteria Clamydiamicrovirus and Bdellomicrovirus:

intracellular parasitic bacteria. Spiromicrovirus: Spiroplasma.

D Protein

Procapsid Virion

ssDNA

B Protein

H Protein F Protein

G Protein

J Protein

 2010

Swiss Institute of Bioinformatics T=1

8 Myoviridae

Structure
Myoviruses are not enveloped and consist of a head and a tail sepa­
rated by a neck. The head has icosahedral symmetry, while the tail
is tubular and has helical symmetry. The capsid that constitutes the
head is made up of 152 capsomers. The head has a diameter of
50-110nm; the tail is 16-20nm in diameter. The tail consists of a
central tube, a contractile sheath, a collar, a base plate, six tail pins
and six long fibers. Tail structure is similar to tectiviridae, but dif­
fers in the fact that a myovirus’ tail is permanent. Contractions of

the tail require ATP. When the sheath is contracted, it measures

10 ­15 nm in lengthicosahedral capsid, circular ssDNA.

Host

Myoviruses, being bacteriophages, infect bacteria. The most com­

monly infected bacteria is Escherichia coli. Myoviruses are viru­

lent phages, meaning they do not integrate their genetic material

with their host cell’s, and they usually kill their host cell. Others

are Bdellovibrio, Chlamydia, Enterobacteria, Spiroplasma.