General MicrobiologyGroup 1

Chimi Seldon Dorji

Sangay Wangmo

Tek Bahadur Powdel

Sang Dorji Tamang

Hem Raj Subba

Norbu ( 14/04/2010)

Definition

•Study of living organism of microscopic size

Eg.:Bacteria, fungi, algae, protozoa, and the infectious agents called viruses.

•Concerned with their form, structure, reproduction, physiology, metabolism and classification

•Study of their distribution in nature, relationship to each other and to other living organisms, effects on human beings, animals and plants

Micro-organisms

•Some are beneficial while others are detrimental

Example: Some micro-organisms are involved in making of yogurt, cheese and wine, in production of penicillin, interferon and alcohol, processing of domestic and industrial wastes

•On the other hand they can cause disease, spoil food and deteriorate materials like iron pipes, glass lenses and wood pilings.

•Unicellular and multi cellular

•Single cell performs all the life processes

•higher organisms are composed of many cells arranged in tissues and organs that perform specific functions

Characteristics Description

Morphological

Characterisics

Study of individual cells of a pure culture

Size expressed in micrometers (µm)

1 µm=.001mm=.00004 in

Examination requires use of a high power microscope (1000

diameters)

Chemical

Characteristics

M.Cells contain variety of organic compounds

characteristic chemical composition

qualitative and quantitative differences in composition

among species

Eg. Lipopolysaccharide is present in Gram negative bacteria and

not in Gram positive bacteria, algal and fungal cell wall are

different from those of bacteria, viruses are distinguished by

RNA and DNA

Characteristics of Microorganisms

Characteristics Description

Cultural

Characteristics

Specific growth requirements; culture medium,medium

containing inorganic and organic compounds, natural

substances,some can be propogated only in living host or living

cells,

some grow at temp. above 40ºC,some cannot grow above

20ºC,some at 37ºC, some need O2 while others dont need it,

bacteria like cyanobacteria require light while growth is

inhibited by light in some others

Metabolic

Characteristics

Life processes involves complex chemcal reactions-

metabolism, obtain energy by absorbing light or by oxidizing

various organic and inorganic substances.

Characteristics Description

Antigenic Characteristics Chemical compounds - antigens

Blood serum proteins, antibodies

respond to antigens

Genetic Characteristics •DNA base composition•The sequence of nucleotide bases in the DNA

Pathogenicity Ability to cause the disease

Ecological Characteristics Habitat is important in characterizing organismsEg. Marine Vs freshwater Oral cavity Vs intestinal tract

Branches of Microbiology

1. Bacteria 2. Virus3. Fungi: Molds4. Fungi: Yeasts5. Protozoa6. Algae

(1) Bacteria

(2) Viruses

(3) Fungi: Molds

(4) Fungi: Yeasts

(5) Protozoa

(6) Algae

Branches Size Important Characteristics Practical Significance

Bacteria 0.5-1.5μm prokaryotic, unicellular, simple

internal structure, grow on

artificial laboratory media,

asexual reproduction by simple

cell division

some cause disease, some

help in natural cycling of

elements, manufacture of

compounds

spoils and makes food

Viruses 0.015-.2μm don’t grow in laboratory media,

requires living cells for

reproduction, obligate parasites,

electron microscope to see it

cause diseases in human,

plants, animals and infect

other microorganisms

Fungi:

Molds

2.0-10μm Eukaryotic, multi cellular can

be cultivated in the laboratory,

reproduction by sexual and

asexual processes.

decomposition, industrial

production of chemicals,

penicillin, causes diseases

in humans, plants &

animals

Branches Size Important Characteristics Practical Significance

Fungi: Yeasts 5.0-10μm Eukaryotic, unicellular, cultivated

in laboratory, reproduction by

sexual, asexual and budding

processes

alcoholic beverages, food

supplement, cause disease

Protozoa 2.0-200μm Eukaryotic, unicellular, cultivated

in laboratory, reproduction by

sexual and asexual processes,

parasites

food for aquatic animals,

some cause disease

Algae 1.0μm-

many feet

Eukaryotic, unicellular &

multicellular, aquatic,

chlorophyll, reproduction by

sexual and asexual processes

production of food in

aquatic environment,

medicines, food

supplement, source of

agar, toxic substance

production

Microbial Classification

Classification •bringing order to the bewildering variety of organism in nature.•Pure culture- a population of micro-organism

•a culture consist of single kind of micro organism(one living species), regardless of the number of individuals, in an environment free of other living organism is called pure culture.

Classification (1) Virus

The Baltimore classification

Classification of virus into families depending on their type of genome

(DNA, RNA, single-stranded (ss), double-stranded (ds) etc.) and their

method of replication.

(2)Bacteria

shape, either gram positive or gram negative, based on whether they

take up the gram stain that is commonly used to make them easier to

see under the microscope. live in the presence of oxygen (aerobic) or

require the absence of oxygen (anaerobic).

Gram Positive Bacteria (e.g., Staphylococcus aureus)

The walls of gram positive bacteria have more peptidoglycans (the large

molecular network of repeating disaccharides attached to chains of four or

five amino acids) than do gram-negative bacteria. Thus, gram-positive

bacteria retain the original violet dye and cannot be counterstained.

Gram Negative Bacteria(e.g., Escherichia coli )

have thinner walls, containing an outer layer of lipopolysaccharide, which is

disrupted by the alcohol wash. This permits the original dye to escape,

allowing the cell to take up the second dye, or counterstain. Thus, gram-

positive bacteria stain violet, and gram-negative bacteria stain pink.

Gram Positive Bacteria

Cell Shape Characteristics Genus Family

Cocci cells in irregular

clusters

staphylococcus

Micrococcus

Sarcina

Micrococcaceae

Cells in chains Streptococcus

Leuconostoc

Streptococcaceae

Bacilli Aerobic Sporing Bacillus Bacillaeceae

Anaerobic Sporing Clostridium

Lactic fermentation Lactobacillus Lactobacillacaeae

Propionic

fermentation

Propionibacterium Propioni-

bacteriaceae

Cell Shape Characteristics Genus Family

Oxidative,

weakly

fermentative

Corynebacterium

Listeria

Erysipelothrix

Cell Shape Characteristics Genus Family

Cocci Aerobic Neisseria

Veilonella

Neisseriaceae

Coccobacilli Brucella, Bordetella

Pasteurella

Haemophilus

Brucellaceae

Bacilli Facultative

anaerobic, motile

with peritrichous

flagella or

immotile

Escherichia,

Shigella,

Salmonella, Proteus,

Erwinia, Yersinia,

Enterobacter,

Serratia

Entero-

bacteriaceae

Gram Negative Bacteria

Cell Shape Characteristics Genus Family

Aerobic, motile with

peritrichous flagella or

immobile

Azotobacter

Rhizobium

Azotobacteraceae

Rhizobiaceae

Aerobic, motile with

polar flagella

Nitrosomonas,

Nitrobacter,

Thiobacillus

Nitrobacteraceae

Pseudomonas,

acetobacter,

legionella

Pseudomona-

daceae

Facultative anaerobic

with polar flagella

Campylobacter,

Zymomonas,

Aeromonas

Curved rods with

polar flagella

Vibrio, Spirillum,

Desulfovibrio

Spirillaceae

Main Requirements for bacterial culture

1. Moisture

2. Warmth and Temperature

3. Time

4. pH level

5. Oxygen

6. Competition

How to grow/culture bacteria?

Things required•Agar •Cooking thermometer •Small cooking pot •Petri dishes •Sterile cotton swabs •Warm dark cupboard •Book on bacteria cultures

Step 1

Mix the agar according to the manufacturer's instructions. Agar is a bit like Jell-o and the ingredients will need to be heated to precise temperatures. Make certain that you have a clean cooking thermometer handy.

Step 2

Open a petri dish and pour just enough agar into the dish to cover the bottom completely. Put the lid back on immediately and set the dish aside until the agar firms. Fill each dish the same way, never leaving the top of the dish off any longer than absolutely necessary. Once the agar hardens you may store the dishes in the refrigerator upside down to avoid the possibility of any airborne bacteria getting into the dishes.

Step 3

Remove the petri dishes from the refrigerator only when you are ready to use them. Open your sterile cotton swab package and rub the cotton swab on a surface you wish to test for bacteria, such as a countertop. Open a petri dish and rub your swab gently across the surface of the agar in an "S" pattern. Close the lid on the petri dish.

Step 4

Set the dish in a warm dark cupboard for three to four days Step 5

Remove the dish from the cupboard. There is no need to open the dish. Observe the bacteria colonies through the top of the dish. Record their color, shape and anything else distinguishing. Look in a bacteria book or on the Internet for illustrations that match the bacteria you have cultured.

Step 6

Destroy your cultured bacteria once you have identified it. Pour 1 tbsp. of bleach into the petri dish and then seal the dish closed with packing tape, put the dish in a baggie, seal it and throw away.

Scope of Microbiology

1.Medical biologyCausative agents of disease; diagnostic procedures; diagnostic procedures for identification of causative agents, preventive measures

2.Aquatic Microbiology

Water purification, microbiological examination, biological degradation of waste,ecology

3.Aeromicrobiology

Contamination and soilage; dissemination of diseases

4.Food microbiology

Food preservation and preparation; foodborne diseases and their prevention

5.Agricultural microbiology

Soil fertility, plant and animal diseases

6.Industrial microbiologyProducton of medicinal products such as antibodies and vaccines; fermented beverages; industrial chemicals, production of proteins and hormones by genetically engineered microorganisms.

7.ExomicrobiologyExploration for life in the outer space

8.Geochemical microbiologyCoal, mineral and gas formation; prospecting for deposits of coal, oil, and gas; recovery of minerals from low-grade ores