Fundamental Food Microbiology, Third Edition - Fuad Fathir

CHARACTERISTICS OF PREDOMINANT MICROORGANISMS IN FOOD 25
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acid). Can also spoil some fruits (rot). Widely distributed in plants and in places
where alcohol fermentation occurs. Important species: Acetobacter aceti.
Gluconobacter. Many characteristics of this group similar to those of Acetobacter.
Gluconobacter oxydans causes spoilage of pineapples, apples, and pears (rot).
Acinetobacter. Rods (1 ¥ 2 mm); occur in pairs or small chains; show twitching motility
because of the presence of polar fimbriae; strictly aerobic and grow between 20
and 35�C. Found in soil, water, and sewage. Important species: Acinetobacter
calcoaceticus.
Morexella. Very short rods, frequently approaching coccoid shape (1 ¥ 1.5 mm); occur
singly, in pairs, or short chains; may be capsulated; twitching motility may be
present in some cells; optimum growth at 30 to 35�C. Found in the mucous
membrane of animals and humans. Important species: Morexella lacunata.
Alteromonas. Most currently assigned Alteromonas species are of marine origin and
might be present in foods of marine origin. Need 100 mM NaCl for optimum
growth (unlike Pseudomonas). Because Alteromonas putrefacience (species
recently reclassified as Shewanella putrifacience) has many characters similar to
those of Pseudomonas, it was previously designated as Pseudomonas putrefacience.
Strains important in fish and meat spoilage. Psychrotrophs.
Flavobacterium. Rods with parallel sides (0.5 ¥ 3 mm); nonmotile; colonies colored;
some species psychrotrophs. Cause spoilage of milk, meat, and other protein foods.
Species: Flavobacterium aquatile.
Alcaligenes. Rods or coccobacilli (0.5 ¥ 1 mm); motile; present in water, soil, or fecal
material; mesophiles. Cause spoilage of protein-rich foods. Species: Alcaligenes
faecalis.
Brucella. Coccobacilli (0.5 ¥ 1.0 mm); mostly single; nonmotile. Different species
cause disease in animals, including cattle, pigs, and sheep. They are also human
pathogens and have been implicated in foodborne brucellosis. Brucella abortus
causes abortion in cows.
Psychrobacter. The genus was created in 1986 and contains one species — Psychrobacter
immobilis. Coccobacilli (1 ¥ 1.5 mm) and nonmotile. Can grow at 5�C or
below, show optimum growth at 20�C, and unable to grow at 35�C. Found in fish,
meat, and poultry products.
2. Gram-Negative Facultative Anaerobes
Citrobacter. Straight rods (1 ¥ 4 mm); single or in pairs; usually motile; mesophiles.
Found in the intestinal contents of humans, animals, and birds, and in the environment.
Included in the coliform group as an indicator of sanitation. Important
species: Citrobacter freundii.
Escherichia. Straight rods (1 ¥ 4 mm); motile or nonmotile; mesophiles. Found in the
intestinal contents of humans, warm-blooded animals, and birds. Many strains
nonpathogenic, but some strains pathogenic to humans and animals and involved
in foodborne diseases. Used as an indicator of sanitation (theoretically nonpathogenic
strains) in coliform and fecal coliform groups. Important species: Escherichia
coli.
Enterobacter. Straight rods (1 ¥ 2 mm); motile; mesophiles. Found in the intestinal
contents of humans, animals, birds, and in the environment. Included in the
coliform group as an indicator of sanitation. Important species: Enterobacter aerogenes.