HISTORICAL DEVELOPMENTS,

Microorganisms important in food BACTERIA- general

characteristics, classification and

importance

Presented byDeepika Rana

1601M.Sc. Microbiology (3rd Sem)

M.D. University, Rohtak

HISTORICAL DEVELOPMENTS

• Although it is extremely difficult to pinpoint the precise beginnings of human awareness of the presence and role of microorganisms in foods, the available evidence indicates that this knowledge preceded the establishment of bacteriology or microbiology as a science.

• Some of the more significant dates and eventsin the history of food preservation, food spoilage, food poisoning,are

Year Event

1782 Canning of vinegar was introduced by a Swedish chemist.

1813 Use of SO2 as a meat preservative is thought to have originated around this time

1839 Tin cans came into wide use in the United States.

1840 Fish and fruit were first canned.

1853 R. Chevallier-Appert obtained a patent for sterilization of food by autoclaving.

1854 Pasteur began wine investigations. Heating to remove undesirable organisms was introduced commercially in 1867- 1868.

1855 Grim wade in England was the first to produce powdered milk.

1865 The artificial freezing offish on a commercial scale was begun in the United States. Eggs followed in 1889.

1880 The pasteurization of milk was begun in Germany.

1882 Krukowitsch was the first to note the destructive effects of ozone on spoilage bacteria.

1890 Mechanical refrigeration for fruit storage was begun in Chicago.

1907 E. Metchnikoff and co-workers isolated and named one of the yogurt bacteria, Lactobacillus bulgaricus.

1908 Sodium benzoate was given official sanction by the United States as a preservative in certain foods.

1928 The first commercial use of controlled atmosphere storage of apples was made in Europe (first used in New York in 1940)

1950 The D value concept came into general use.

Year Event

1680 Leeuwenhoek was the first to observe yeast cells.

1780 Scheele identified lactic acid as the principal acid in sour milk.

1857 Pasteur showed that the souring of milk was caused by the growth of organisms in it.

1873 The first reported study on the microbial deterioration of eggs was carried out by Gayon.— Lister was first to isolate Lactococcus lactis in pure culture.

1888 Miquel was the first to study thermophilic bacteria.

1895 S.C. Prescott and W. Underwood traced the spoilage of canned corn to improper heat processing for the first time.

1915 Bacillus coagulans was first isolated from coagulated milk by B. W. Hammer.

Year Event

1857 Milk was incriminated as a transmitter of typhoid fever by W. Taylor of Penrith, England.

1888 Gaertner first isolated Salmonella enteritidis from meat that had caused 57 cases of food poisoning.

1896 Van Ermengem first discovered Clostridium botulinum.

1906 Bacillus cereus food poisoning was recognized

1937 Paralytic shellfish poisoning was recognized.

1955 Similarities between cholera and Escherichia coli gastroenteritis in infants were noted by S. Thompson.

1960 The production of aflatoxins by Aspergillus flavus was first reported.

BACTERIA important in food general characteristics, classification and importance

Morphological characteristics important in food bacteriology1. Encapsulation2. Formation of endospores3. Formation of cell aggregates

Cultural characteristics important in food bacteriologyBacterial growth in or on food often is extensive enough to make the food unattractive in appearance or otherwise objectionable. Pigmented bacteria cause discolouration on the surface of the food; films may cover the surface of liquid ; growth may make surface slimy; or growth throughout the surface may result in undesirable cloudiness or sediment.

Eight Sources of Bacteria to Foods

Soil and water, Plants/ products, Food utensils, Gastrointestinal tract, Food handlers, Animal feeds, Animal hides, Air and dust

SYNOPSIS OF COMMON FOODBORNE BACTERIA

Acinetobacter (unable to move).

•Gram negative•Rod shaped•Oxidase negative•Strict aerobes•Do not reduce nitrates•Although rod-shaped cells are formed in young cultures, old cultures contain many coccoid shaped cells.•Widely distributed in soil and waters and may be found on many foods, •Especially refrigerated fresh products.

On chromagar

Aeromonas (ae • ro • mo'nas; gas producing).•These are typically aquatic gram-negative rodsformerly in the family Vibrionaceae but now inthe family Aeromonadaceae.•As the generic name suggests, they produce copious quantities of gas from those sugars fermented. •They are normal inhabitants of the intestines of fish, and some are fish pathogens. •The mol% G + C content of DNA is 57-65.

Food market egg salads have been reported contaminated with Aeromonas bacteria.

Alcaligenes (alkali producers).•Although gram negative, these organisms•sometimes stain gram positive. •They are rods that do not, as the generic name suggests, ferment sugars but instead produce alkaline reactions, especially in litmus milk. •Nonpigmented, they are widely distributed in nature in decomposing matter of all types. Raw milk, poultry products,•and fecal matter are common sources. •The mol% G + C content of DNA is 58-70, suggesting that the genus is heterogeneous.•Curdlan consists of β-(1,3)-linked glucose residues and forms elastic gels upon heating in aqueous suspension. The production of curdlan by Alcaligenes faecalis is being developed to be used in gel production as well.

Alteromonas (al • te • ro • mo'nas; anothermonad). These are marine and coastal water inhabitantsthat are found in and on seafoods; allspecies require seawater salinity for growth. They are gram-negative motile rods that are strict aerobes.

Citrobacter slow lactose-fermenting, gram-negative rods. All members can use citrate as the solecarbon source. C.freundii is the most prevalentspecies in foods, and it and the other species are not uncommon on vegetables and fresh meats.

•Arcobacter (Ar'co • bac • ter; L. arcus, bow).•They are gram-negative•curved or S-shaped rods •except they can grow at 15°C and are aero tolerant. •They are found in poultry, raw milk, shellfish, and water; and in cattle and swine products.•These oxidative and catalase-positive organisms cause abortion and enteritis in some animals, and the latter in humans is associated with A. butzleri.

Arcobacter Septicus Bacteria, SEM

Molluscs filter-feed, contaminated sea water could result in the bioaccumulation of A. butzleri

Bacillus•gram-positive•sporeforming rods •are aerobes•most are mesophiles, psychrotrophs and thermophiles• Two pathogens: B. anthracis (cause of anthrax) and B. cereus. •Although most strains of the latter are nonpathogens, some cause foodborne gastroenteritis. •grow as low as about 35°C to 700C, and over the pH range 2 to 6.•B.cereus is a food borne pathogen•Growth of B. cereus in pasteurised milk is considered the main limiting factor determining the shelf life of this food product. Too high levels of B. cereus in pasteurized milk before the end of shelf life or prolonged refrigerated storage cause common structural defects known as sweet curdling and bitty cream

Campylobacter•gram-negative, •spirally curved rods •Formerly classified as vibrios. •Microaerophilic to anaerobic.•Campylobacter jejuni is the most common cause of bacterial foodborne illness in the United States.

Clostridium (spindle). •Anaerobic sporeforming rods•widely distributed in nature•C. perfringens food poisoning and botulism Mesotrophic, psychrotrophic, and thermophilic

Corynebacterium (club). •True coryneform genera •gram-positive, rod-shaped•involved in the spoilage of vegetable and meat products. •Most are mesotrophs, although psychrotrophs are known, and one, C. diphtheriae, causes diphtheria in humans.

Erwinia •Gram-negative•enteric rods •associated with plants, where they cause bacterial soft rot

Flavobacterium •These gram-negative rods are characterized by their production of yellow to red pigments on agar and by their association with plants. •Some are mesotrophs, and others are psychrotrophs, where they participate in the spoilage of refrigerated meats and vegetables.

Leuconostoc•gram-positive, catalase-negative cocci•Heterofermentative•produce lactic acid and diacetyl•Leuconstoc mesenteroides used primarily in sauerkraut production•In fermented milk and meat products, diacetyl is responsible for butter flavor. •L.carnosum produces bacteriocins, and these are used to inhibit Listeria monocytogenes in dairy and meat products.

Lactobacillus •gram-positive,•catalase-negative rods that often occur in long chains. •They typically occur on most, if not all, vegetables, along with some of the other lactic acid bacteria.•Their occurrence in dairy products is common. •L. suebicus, was recovered from apple and pear mashes; it grows at pH 2.8 in 12-16% ethanol.•Miso, tempeh, umeboshi, which is a type of pickled plum, and pickles along with a number of other fermented vegetables, can contain active cultures of lactobacilli, but only if they're not pasteurized or subjected to high heat.

Micrococcus •Gram positive cocci•Catalase positive, •produce pink to orange-red to red pigments,•whereas others are nonpigmented. •Grow at high levels of NaCl, •mesotrophs, psychrotrophic also known. •M.luteus used in cheese production

Listeria•Gram-positive,•Nonsporing rods •identical cell walls, fatty acid, and cytochrome composition.

Proteus (pro'te • us). •Enteric gram-negative rods •aerobic pleomorphic,•Motile •Produce swarming growth on moist agar plates•Present in the intestinal tract of humans and animals. •Isolated from a variety of vegetable and meatproducts, especially those that undergo spoilage at temperatures in the mesophilic range.

Pseudomonas (false monad).•Gram-negative rods •Largest genus of bacteria that exists in fresh foods. •Typical of soil and water bacteria •Widely distributed among foods, especially vegetables, meat, poultry, and seafood products. •Bring about the spoilage of refrigerated fresh foods because many species and strains are psychrotrophic.•Some are notable by their production of watersoluble, blue-green pigments, whereas many other food spoilage types are not.

P. aeruginosa growing on Skim Milk Agar.

Shigella All members are human enteropathogens.

Staphylococcus (grapelikecoccus). These gram-positive, catalase-positivecocci include S. aureus, which causes severaldisease syndromes in humans, includingfoodborne gastroenteritis.

Serratia•Gram-negative rods•belong to Enterobacteriaceae •aerobic and proteolytic, •Produce red pigments on culture media and in certain foods, although nonpigmented strains are not uncommon. •S. liquefaciens most prevalent of the foodborne species; it causes spoilage of refrigerated vegetables and meat products.

•Vibrio (vib'ri • o). •These gram-negative straight or curved rods are members of the family Vibrionaceae. •Several species cause gastroenteritis and other human illness;•V. parahaemolyticus typically causes non-bloody diarrhea. •In persons with liver disease, cancer, or another immune-compromising condition, V. vulnificus typically infects the bloodstream, causing a life-threatening illness. •Half of the infections are fatal, and death can occur within two days. •Transmission by raw shellfish, enter the body via a wound that is exposed to warm seawater.

Yersinia (yer • si'ni • a). This genus includes the agent of human plague, Y.pestis, and at least onespecies that causes foodborne gastroenteritis,Y. enterocolitica.

Yersinia pestis rod-shaped bacteria in the bubonic form

Acidophilus milk is made with Lactobacillus acidophilus.

Butter is made from pasteurized cream, to which a lactic acid starter has been added. The starter contains, for example, Streptococcus cremoris or S. lactis, but requires Lactobacillus diacetylactis to give it its characteristic flavor and odor.

Cheese is often made with Streptococcus and Lactobacillus bacteria. Fermentation lowers the pH, thus helping in the initial coagulation of the milk protein, as well as giving characteristic flavors. Lactococcus lactis and Leuconostoc cremoris are used most often. Propionibacterium shermanii is used in the preparation of swiss cheese.

Kefir includes many different microbes, including yeasts, lactobacilli, lactococci, and leuconostocs. Depending on geographical locations, the precise types of microbes will vary. Yogurt usually requires the addition of Lactobacillus bulgaricus, Lactococcus thermophilus, and/or Streptococcus thermophilus to the milk.

Glutamic acid requires Corynebacterium glutamicum for its formation. By growing C. glutamicum on limited amounts of biotin(cofactor for lipid synthesis), it causes the bacterial membrane to leak sufficient quantities of glutamic acid.

Lysine -- The bacterium, Brevibacterium flavum is used in the industrial biosynthesis of lysine. Mutants no longer susceptible to feedback inhibition have been isolated to be used industrially to increase the yield of amino acids.

Soy sauce is made from a mixture of soy beans and rice fermented by Lactobacillus delbrueckii

•Meat products, like salami and bologna sausages, require some fermentation with Pediuococcus cerevisiae, Lactobacillus plantarum and some members of the genus Bacillus. Izushi (sushi), a Japanese delicacy made from a mixture of fish, rice, and other vegetables is produced by fermentation with lactobacilli.

•Sauerkraut-making requires the bacteria Leuconostoc mesenteroides and Lactobacillus brevis to ferment sugars that provide a variety of such organic products as lactic acid, acetic acid, ethanol, and mannitol. Later a 'homofermentative' bacteria, Lactobacillus plantarum takes over, producing only lactic acid. Later, Enterococcus faecalis and Pediococcus cerevisiae assume the fermentation process if the salt brine is not what it should be.

•Dill pickles are simply fermented cucumbers. Streptococci starts the process of fermentation, but as the pH level falls, leuconostoc and pediococcus species, as well as Lactobacillus plantarum continue the process.

•Olives are edible only after fermentation with Lactobacillus plantarum and Lactobacillus mesenteroides.

•Coffee and chocolate require Erwinia dissolvens, leuconostoc, and lactobacillus species plus the yeasts of the genus Saccharomyces to remove the tough outer coats. The microbes confer the characteristic taste to cocoa and chocolate. It is thought that the chocolate provides protection for the bacterium as it passes through the acidic environment of the stomach. This was observed when higher incidents of illness were reported in children.

Sauerkraut Dill pickles

Fermented olives Chocolate and coffee

References 1. Bacteria and Viruses | FoodSafety.govhttps://www.foodsafety.gov/poisoning/causes/bacteriaviruses/2. Bacteria in food production | effcawww.effca.org/content/bacteria-food-production3. List of microorganisms used in food and beverage preparation ...https://en.wikipedia.org/.../List_of_microorganisms_used_in_food_and_beverage_pre...4. Modern Food Microbiology, sixth edition, James M. Jay(2000)

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