Fundamental Food Microbiology, Third Edition - Fuad Fathir

16 FUNDAMENTAL FOOD MICROBIOLOGY
Evolutionary relationships among viruses, if any, are not known. Their classification
system is rather arbitrary and based on the types of disease they cause (such
as the hepatitis virus, causing inflammation of the liver), nucleic acid content (RNA
or DNA, single stranded or double stranded), and morphological structures. In food,
two groups of viruses are important: the bacterial viruses (bacteriophages) of starter
culture bacteria and some foodborne pathogenic bacteria, and the human pathogenic
viruses associated with foodborne diseases.
III. NOMENCLATURE
The basic taxonomic group in bacteria, yeasts, and molds is the species, and each
species is given a name. 1–3 The name has two parts (binomial name): the first part
is the genus name and the second part is the specific epithet (adjective). Both parts
are Latinized; when written, they are italicized (or underlined), with the first letter
of the genus written in a capital letter (e.g., Saccharomyces cerevisiae, Penicillium
roquefortii, and Lactobacillus acidophilus). A bacterial species can be divided into
several subspecies (subsp. or ssp.) if the members show minor but consistent differences
in characteristics. Under such conditions, a trinomial epithet (subspecific
epithet) is used (e.g., Lactococcus lactis ssp. lactis or Lactococcus lactis ssp. cremoris).
In some instances, ranks below subspecies are used to differentiate strains
recognized by specific characters (e.g., serovar, antigenic reaction; biovar, producing
a specific metabolite; and phagovar, sensitive to a specific phage). Such ranks have
no taxonomic importance but can be practically useful (e.g., Lactococcus lactis ssp.
lactis biovar diacetilactis is a Lactococcus lactis ssp. lactis strain that produces
diacetyl, an important flavor compound in some fermented dairy products). Each
strain of a species should be identified with a specific strain number, which can be
alphabetic or numeric or a mixture of both (e.g., Pediococcus acidilactici LB923).
At the family level, bacterial names are used as plural adjectives in feminine gender
and agree with the suffix “aceae” (e.g., Enterobacteriaceae). The species and strains
in a genus can be represented collectively, either using “spp.” after genus (e.g.,
Lactobacillus spp.) or plural forms of the genus (e.g., lactobacilli for Lactobacillus;
lactococci for Lactococcus; leuconostocs for Leuconostoc, or salmonellae for Salmonella).
The scientific names of bacteria are given according to the specifications of the
International Code of Nomenclature of Bacteria. The International Committee on Systematic
Bacteriology of the International Union of Microbiological Association examines
the validity of each name and then publishes the approved lists of bacterial names
from time to time. A new name (species or genus) must be published in the International
Journal of Systematic Bacteriology before it is judged for inclusion in the approved
list. Any change in name (genus or species) has to be approved by this committee.
When writing the name of the same species more than once in an article, it is
customary to use both genus and specific epithet the first time and abbreviate the
genus name subsequently. In the Bergey's Manual of Systematic Bacteriology, only
the first letter is used (e.g., Listeria monocytogenes and then L. monocytogenes).
The same system is used in most publications in the U.S. However, it creates