Food Micro Organisms- Characterstics

Micro- Organisms

·         Study of micro-organisms is called micro biology.

·         Uses nutrients, eliminate waste, grow & reproduce.

·         Compound microscopes- 1500 times

·         Electron Microscope- 500000 times

Five groups of microbes

        i.            Viruses

      ii.            Bacteria

    iii.            Fungi- Molds & yeasts

    iv.            Algae

      v.            Parasites

Viruses:-

        I.            Smallest form

     II.            Grow & reproduces inside living cells

   III.            Strictly parasitic

  IV.            Are Pathogenic

     V.            Very minute i.e. 1/10 to 1/100 of bacteria

  VI.            0.015 - .2 micrometer. (1 micrometer= 1/1000 of a millimeter)

VII.            Virus attacks as it sticks with the plant, animal & bacterial cells & releases its nucleus inside cells. It continues to multiply & when sufficient number of cells are formed, the specific cell bursts & virus attacks other cells.

VIII.            Viral food borne diseases are like hepatitis.

Bacteria:-

        I.            Unicellular & microscopic.

     II.            Different shape, size & activity, so identified & named on the basis of morphology i.e. shape, size & cell arrangements as with flagella, capsule or slime layer.

   III.            Size varies from 0.2 micron meter to 10micron meter.

Types: Rod shaped, spherical or round, spiral bacteria or comma.

Rod shaped:

a.       They have flagella & some spices can form endospores.

b.      Coliform bacteria in the large intestine also called colon is rod form.

c.       Presence in food or water signifies faecal contamination.

d.      Typhoid, dysentery & clostridium food poisoning.

Spherical or round:

a.       Also called cocci.

b.      Present as pair of called-diplococcic

c.       Chains of cocci- streptococci

d.      Irregular clusters- streptococci

e.       Tetrads or cubes of four to eight cocci cause spoilage of food.

Spiral shaped:

a.       Called spirilla

b.      Cause syphilis

Comma bacteria:

a.       also called vibrios

b.      cause cholera

        I.            At favorable conditions bacteria reproduces by fission.

     II.            Every full grown cell divide into two every 20- 30 minutes.

   III.            A single cell can reproduce to two million cells in 7 hours.

  IV.            At unfavorable conditions i.e. end of food the spore forming bacteria forms endospores while others die.

     V.            This is large group of microbes with most concerns as this can multiply enormous at room temperature.

  VI.            Most food poisonings are bacterial origins.

Fungi:-

·         Lower plants which lack chlorophyll.

·         Saprophytic in nature.

·         Multicellular plants but body is not differentiated into roots, stems & leaves.

·         Size varies from microscopic yeasts to large mushrooms.

Yeasts:

·         Single celled, require food as carbohydrates & moisture for growth.

·         Found is soil n dust.

·         Size 5-10 micrometer.

·         Oval, lemon shaped & elongated.

·         Reproduce by polar budding.

·         Can grow in refrigeration temperatures.

·         Capable of anaerobic respiration to convert sugars into carbon dioxide & alcohol.

·         Saccharomyces cerevisiae is used for fermentation in bakeries & breweries.

·         Can grow on surfaces of high acid & salt as on pickles & chutneys.

·         Identified by slimy & Powderly film or cloudy substances on the liquids or by the presence of bubbles & an alcoholic smell.

·         They require a moisture level of 20% to grow on products such as jams, dried fruits, jellies etc.

Molds:

·         Multicellular organisms seen as fuzzy, velvety or powdery patches on the surfaces of food with very low moisture.

·         Body is thread like or filamentous called hyphae.

·         Entire plant is called mycelium.

·         Hyphae can grow with in the food or above in the air.

·         They reproduce by spores formation.

·         When spore head matures, spores are spread in the air.

·         2-10 micron to several meters.

·         Produce toxins.

·         Aspergillus flavus produces aflatoxin grown on inadequately dried peanuts.

Algae:-

·         Found naturally in water.

·         Both unicellular & multicellular.

·         Contain chlorophyll & are green, perform photosynthesis.

·         Size- 1 micrometer to many meters.

·         Unpleasant odor and are slimy.

·         Most forms are non-pathogenic.

·         Unicellular algae are important for water purification & sewage disposal plants.

·         Primary producers of food for aquatic life.

·         Gonyaulax catenella is a pathogenic algae.

·         Multicellular algae are a source of agar for making culture medium.

Parasites:-

·         Dependent on living host for growth & reproduction.

·         Can be single celled as Entamoeba histolytica causing amobic dysentery in humans.

·         Can be multi-celled animals/worms as taenia solium/ pork tape worm found in intestines of human.

·         Size varies from 2 micron to many feet.

·         Considered as micro-organisms as their cysts or eggs are microscopic and are transmitted through infected food or poor personal hygiene.

·         Amoebic dysentery or amoebiasis is caused by sewage contaminated water or eating root salads grown on soil applied with manure/ excreta fertilizer.

·         Amoebic dysentery or amoebiasis is common in India whereas trichinosis is common in countries having pork meat in large quantities caused by parasitic worm Trichinella spiralis.