Characteristics of Predominant Microorganisms in Food  ◾  29
Osmophilic Bacteria
These are bacteria that can grow in a relatively higher osmotic environment than what is needed
for other bacteria. Some species from genera Staphylococcus, Leuconostoc, and Lactobacillus are
included in this group. They are much less osmophilic than yeasts and molds.
Gas-Producing Bacteria
These are bacteria that produce gas (CO 2 , H 2 , H 2 S) during metabolism of nutrients. Species from
genera Leuconostoc, Lactobacillus, Propionibacterium, Escherichia, Enterobacter, Clostridium, and
Desulfotomaculum are included in this group.
Slime Producers
These are bacteria that produce slime because they synthesize polysaccharides. Some species or
strains from Xanthomonas, Leuconostoc, Alcaligenes, Enterobacter, Lactococcus, and Lactobacillus are
included in this group.
Spore Formers
These are bacteria having the ability to produce spores. Species from Bacillus, Clostridium, and
Desulfotomaculum are included in this group. They are further divided into aerobic spore formers,
anaerobic spore formers, flat sour spore formers, thermophilic spore formers, and sulfide-producing
spore formers.
Aerobes
These are bacteria that require oxygen for growth and multiplication. Species from Pseudomonas,
Bacillus, and Flavobacterium are included in this group.
Anaerobes
These are bacteria that cannot grow in the presence of oxygen. Species from Clostridium are
included in this group.
Facultative Anaerobes
These are bacteria that are able to grow in both the presence and absence of oxygen. Lactobacillus,
Pediococcus, Leuconostoc, enteric pathogens, and some species of Bacillus, Listeria, Salmonella,
Serratia, and coliforms are included in this group.
Coliforms
Species from Escherichia, Enterobacter, Citrobacter, and Klebsiella are included in this group. They
are used as an index of sanitation.