Home Causes Prevention Food Poisoning Spoilage Organisms Lab 36


(For words in bold, please see the definitions section. Descriptions of the organisms follow.)

Organism Types of food it spoils Type of spoilage



Alternaria tomatoes brown/black mold rot
Aspergillus bread black mold
maple sap and syrup black mold
fresh fruits and vegetables black mold rot
cured meat black mold
grains, nuts black mold rot (see also aflatoxins)
Botrytis fresh fruits and vegetables gray mold rot
Candida butter yeasty
concentrated juices yeasty
Cladosporium tomatoes brown/black mold rot
Claviceps purpura corn, grain ear rot (see also ergotism)
Fusarium tomatoes pink mold rot
corn pink ear rot (see also fumonisins)
Geotrichum butter yeasty
Penicillium bread blue-green mold
maple sap and syrup blue-green mold
cured meat blue-green mold
eggs blue-green mold
Rhizopus bread black mold
cured meat black mold
fresh fruits and vegetables soft rot
Rhodotorula pickles, sauerkraut film yeasts, pink yeasts
Saccharomyces maple sap and syrup yeasty
concentrated juices yeasty
condiments yeasty
Stemphylium tomatoes brown mold rot
Zygosaccharomyces maple sap and syrup yeasty



Acetobacter concentrated orange juice “off” flavor
wines makes vinegar
fresh fruits and vegetables acidifying
Aeromonas eggs souring
Alcaligenes fresh/raw meat putrefaction
fish putrefaction
eggs colorless rot
poultry slime, odor
raw milk ropy
Bacillus bread slime
condiments slime
Pasteurized milk ropy
Clostridium fresh/raw meat putrefaction
condiments souring
Pasteurized milk souring
Corynebacterium vegetables soft rot
Enterobacter aerogenes maple sap and syrup ropy
Erwinia fresh fruits and vegetables soft rot
Escherichia fresh/raw meat putrefaction, slime
Flavobacterium fish putrefaction
raw milk souring
Lactobacillus fresh/raw meat putrefaction
cured meat greening, slime
concentrated orange juice “off” flavor
condiments souring
Pasteurized milk souring
Lactococcus raw milk souring
Leuconostoc cured meat greening, slime
concentrated orange juice “off” flavor
Micrococcus maple sap and syrup pink bacterial growth
fresh/raw meat putrefaction
cured meat souring
Pasteurized milk souring
Proteus fresh/raw meat putrefaction
eggs black rot
Pseudomonas fresh/raw meat putrefaction
cured meat souring, slime
fish discoloration
eggs green rot, colorless rot
poultry slime, odor
fresh vegetables soft rot
butter souring
raw milk ropy
Streptococcus Pasteurized milk souring



Aflatoxins:  fungal toxins of nuts and grains caused by Aspergillus flavus, which act as frameshift mutagens and carcinogens, especially in the liver. back

Ergotism:  toxic condition of improperly stored corn or grains caused by the fungus Claviceps purpura. Cause hallucinations, altered behavior, abortion, and possible death. back

Food poisoning:  microorganismal growth in food that causes illness but usually does not affect appearance and taste.

Food spoilage:  decomposition and/or microorganismal growth on food that affects appearance and taste, but that usually will not cause illness.

Fumonisins:  fungal toxins of corn made by Fusarium moniliforme that, if ingested, cause leukoencephalomalacia in horses, pulmonary edema in pigs, and esophageal cancer in humans. Can be found in corn and in corn-based feeds and foods, such as cornmeal and corn grits, when stored under damp conditions. back

Putrefaction:  decomposition of organic matter, especially protein, by microorganisms, resulting in production of foul-smelling matter. back

Ropy:  see slime. back

Slime:  polysaccharides like dextrans, levans, or starch secreted from some spoilage bacteria (ex: Pseudomonas, Bacillus, Escherichia coli, Leuconostoc). Slimy milk products or other liquids are usually referred to as ropy. back

Soft rot:  mushy or slimy decay of plants, caused by bacteria or fungi. back

Souring:  making acidic or rancid by fermentation. back



Alternaria: Ascomycete. Parasite of leaves, flowers, and the fruit of grains and vegetables; common in soil. back
           Click for a picture of Alternaria

Aspergillus:  Ascomycete. Common black mold found in soil which grows on stored food products such as grain and flour under damp conditions. back

Botrytis:  Ascomycete. Common. Causes diseases on a variety of unrelated crops. Can cause serious losses on certain varieties of grapes, and is the most common form of strawberry mold. back
            Click for a picture of rot in grapes

Candida:  Deuteromycete; yeast. Some species are pathogenic in humans (especially Candida albicans, which can cause thrush, moniliasis, and onychomycosis -- an infection of the nails). Commonly found in the environment, particularly on leaves and flowers, and in water and soil. back
            Click for a picture of Candida albicans

Cladosporium:  Ascomycete. The most common mold in the world, found in soil and on textiles, tomatoes, spinach, bananas, and dead vegetation. back
            Click for a picture of Cladosporium

Claviceps purpura:  Ascomycete. A plant parasite that commonly infects grains such as corn and rye. Causes ergotism, which infects humans and other animals such as cattle. back
            Click for a picture of ergot in wheat

Fusarium:  Ascomycete. Thrives on dead leaves and plants, and lives as a pink mold on shower stall grout, but is most common in soil. Responsible for spoilage of fruits, vegetables, chemicals, water, and aircraft fuel. Produce fumonisins. back

Geotrichum:  Ascomycete; yeast. Found in soil, water, air, and sewage; also found in plants, cereals, and dairy products. May cause bronchial or pulmonary infections in an immunocompromised host. back
               Click for a picture of Geotrichum

Penicillium:  Ascomycete. Commonly spoils cheeses and fruits. Also found in textiles, grains, flour, soil, decaying vegetation, the air, and as a green mold on damp walls. back
                Click for a picture of Penicillium

Rhizopus:  Zygomycete. Found mainly indoors, and on old bread, but also found on organic debris in soil, on decaying fruits and vegetables, and on animal feces. Some species cause serious and often fatal infections in humans, while others are plant pathogens. back

Rhodotorula:  Basidiomycete; yeast. Found in air, soil, lakes, ocean water, and dairy products. May colonize plants and mammals, including humans. back

Saccharomyces:  Ascomycete; yeast. Commonly found in mammals (including humans), birds, fruits, trees, plants, olives, and soil. S. cerevisiae is used in production of bread, wine, and beer. back

Stemphylium:  Ascomycete. Found on decaying vegetation and in soil; grows on farm crops, tomatoes, and grains. back
                Click for a picture of Stemphylium

Zygosaccharomyces:  Ascomycete; yeast. A few species are used in production of some fermented foods. Others are spoilage agents in fruit concentrates and juices, jams, jellies and preserves, as well as in ketchup, salad dressings, relishes and pickles. Saccharophilic. back


Acetobacter:  Found in plants; involved in associative nitrogen fixation in plant root zones and other plant surfaces. Used in production of vinegars. Oxidizes ethanol to acetic acid. Cellulose microfibrils produced by one strain are used as a food thickener. back
                Click for a picture of Acteobacter

Aeromonas:  Gram-negative facultative anaerobes found in brackish, fresh, estuarine, marine, chlorinated, and unchlorinated water supplies worldwide. Sometimes found in diseased animals. A. hydrophila is a free-living water-based pathogen associated with gastroenteritis and cellulitis. back
                Click for a picture of Aeromonas

Alcaligenes:  Gram-negative, non-spore forming bacteria. Produces capsules in milk. A number of strains related to A. faecalis have been used for the production of unnatural amino acids like D-amino acids and others not normally found as part of proteins. back

Bacillus:  Gram-positive, spore-forming bacilli. Facultative anaerobe, motile. Found in soil and growing plants, as well as foods like rice, pasta, spices, and dairy products. B. cereus can cause food poisoning, and some of its enterotoxins closely resemble those of Clostridium perfringens. Some strains have evolved to survive at refrigeration temperatures (4 - 6 degrees C). back

Clostridium:  Gram-positive, spore-forming bacilli. Obligate anaerobe, motile. Can be psychrophilic, mesophilic, or thermophilic. Fermentative. Digest casein and cooked meat. Widely distributed; occur in soil, stream sediments, lakes, coastal waters, the intestinal tracts of fish and mammals, and in the gills and viscera of shellfish. C. botulinum, found in seafood, produces a potent neurotoxin that causes a deadly form of food poisoning. C. perfringens, found in meat, causes a less-severe form of food poisoning that very rarely results in death. back

C. botulinum C. perfringens

Corynebacterium:  Gram-positive, non-spore forming, non-motile, aerobic bacilli. Found in soil. Saprophytes; plant, animal, and human pathogens. C. diphtheriae causes diphtheria, but C. glutamicum, a harmless strain, is used in the industrial production of organic acids for food supplements such as MSG. back

Enterobacter aerogenes:  Gram-negative, motile, aerobic bacilli. Found in soil, water, and sewage; serve as food for protozoans. Normal intestinal flora. Produce lysine, used in the production of breads, breakfast cereals, and other foods. back
                Click for a picture of Enterobacter

Erwinia:  Gram-negative bacilli found in soil and as a plant pathogen. Causes soft rot on stored vegetables. back
                Click for a picture of Erwinia

Escherichia:  Gram-negative bacilli. Found in the intestines of almost all warm-blooded animals, and in many types of environmental waters. E. coli O157:H7 causes food poisoning. back
                Click for a picture of E. coli

Flavobacterium:  Gram-negative, facultative anaerobic bacilli. Non-fermentative. Found in soil, water, plants, foods, and can survive in eyes, urine, and intravenous anesthetics. Fastidious; some strains are opportunistic pathogens in animals and humans, including F. meningosepticum, which causes meningitis. back

Lactobacillus:  Gram-positive, non-spore forming bacilli. Fermentative. Some species are found in the natural microbiota of human oral cavities, intestines, and vaginal tracts. Others are important in the commercial production of lactic acid in food products. Nonpathogenic bacteria which can help prevent infections by other microorganisms. back

Lactococcus:  Gram-positive streptococci. Fermentative. Found in dairy products. L. lactis is used the preparation of cheese, pickled vegetables, beer, wine, some breads and sausages, and other fermented foods. Peptidases made by some species are used to remove bitter tastes from food and to add a natural meat, mushroom, or savory flavor. Nonpathogenic. back

Leuconostoc:  Gram-positive streptococci. Psychrophilic. Lactic acid-producing anaerobic bacteria. Nonpathogenic. Has an inhibitory interaction with Listeria monocytogenes (a pathogenic bacteria found in meat and cheese). Usually found in spoiled, packaged meat. back

Listeria monocytogenes

Micrococcus:  Gram-positive, aerobic diplococci or staphylococci. Saphrophytes, found on human skin, in meat and dairy products, in freshwater, and in soil. Nonpathogenic. back

Proteus:  Gram-negative bacilli. Facultative anaerobes. Motile. Found in plants, human intestinal tracts, soil, eggs, meat, and water. Opportunistic pathogens in humans. back

Pseudomonas:  Gram-negative, aerobic bacilli. Found in soil, water, and surfaces of plants and animals. Some species are pathogens or parasites. P. aeruginosa is especially dangerous to patients with cystic fibrosis, as it creates a lower respiratory infection that is difficult to treat. back

Streptococcus:  Gram-positive streptococci. Thermophilic. Fermentative lactic acid bacteria. S. salivarius is used in yogurt manufacture. Some species are pathogens, but usually not those found in foods. back


Kerr, Thomas J. and Barbara B. McHale. Applications In General Microbiology: A Laboratory Manual. 6th ed. Winston-Salem: Hunter Textbooks, Inc., 2003.
Prescott, Lansing M., John P. Harley, and Donald A. Klein. Microbiology. 5th ed. New York: McGraw-Hill, 2002.
Hygiene Measures in Fruit and Vegetable Storage Warehouses
Microorganisms in foods
Streptococcus salivarius subsp. thermophilus
Micrococcus luteus and M. roseus
Proteus vulgaris, P. mirabilis
Pseudomonas aeruginosa
Lactococcus lactis
Organism profile: Lactococcus lactis
Leuconostoc carnosum
Friendly Bacteria
Food and Biotechnology
Major Groups of Bacteria
Enterobacter aerogenes
The "Bad Bug Book"
B. cereus
Zygosaccharomyces, A Spoilage Yeast Isolated from Wine
Claviceps purpura
Botrytis Bunch Rot or Gray Mold of Grape
Dr. Fungi: The Fungi -- Descriptions
Mold Facts and Experiments
Species of Mold
Food Microbiology