96 4 Taxonomy, Physiology, and Ecology of Aquatic Microorganisms
Fig. 4.27 (The lytic and lysogenic cycles of bacteriophage
replication (from Zourob & Ripp, 2010, with kind permission
from Springer Science+Business Media: Zourob, M. &
Ripp, S. (2010). Bacteriophage-Based Biosensors. In M. Zourob
(Ed.) Recognition Receptors in Biosensors (Fig. 11.3, p. 419).
New York: Springer)
Bacteriophage
Bacterial
chromosome
Cell lysis and release
of progeny
bacteriophage
Lytic Cycle
Lysogenic Cycle
Bacteriophage
genome enters cell
Bacteriophage genome integrates
within the bacterial chromosome as a
prophage and replicates in tendem
with host cell
Prophage can later be excised
from the host chromosome and
enter the lytic cycle
Methods for the Study of Bacteriophages
Because of their small size, bacteriophages are not usually
studied directly as is the case with microorganisms. An
electron microscope is necessary to study viruses, but not
only are electron microscopes expensive, but they require
skilled operators to handle them. Therefore, viruses are
studied indirectly through their effects. The indirect meth
ods used especially for animal and plant viruses, include
the changes (known as cytopathic effects, CPE) they bring
about in the cells in the cell culture in which they are
grown: lysis, altered shape, detachment from substrate,
membrane fusion, altered membrane permeability.
Other methods for studying viruses, particularly of
animals and plants, are serological methods based on
the interaction between virus and antibody produced
specifically against it, detection of viral nucleic acid,
Table 4.18 The structure of RNA viruses (From http://en.wikipedia.org/wiki/Virus_classification; Anonymous 2010 a)
S. No. Virus family Virus genus Virion – naked/enveloped Capsid symmetryType of nucleic acid
- Reoviridae Reovirus, Rotavirus Naked Icosahedral ds
- Picornaviridae Poliovirus, Rhinovirus,
Hepatitis A virus
Naked Icosahedral ss
- Caliciviridae Norwalk virus, Hepatitis E virus Naked Icosahedral ss
- Togaviridae Rubella virus Enveloped Icosahedral ss
- Arenaviridae Lymphocytic choriomeningitis
virus
Enveloped Complex ss
- Retroviridae HIV-1, HIV-2, HTLV-I Enveloped Complex ss
- Flaviviridae Dengue virus, hepatitis C virus,
yellow fever virus
Enveloped Complex ss
- Orthomyxoviridae Influenza virus Enveloped Helical ss
- Paramyxoviridae Measles virus, mumps virus,
respiratory syncytial virus
Enveloped Helical ss
- Bunyaviridae California encephalitis virus,
Hantavirus
Enveloped Helical ss
- Rhabdoviridae Rabies virus Enveloped Helical ss
- Filoviridae Ebola virus, Marburg virus Enveloped Helical ss
- Coronaviridae Corona virus Enveloped Complex ss
- Astroviridae Astro virus Naked Icosahedral ss
- Bornaviridae Borna disease virus Enveloped Helical ss
