3. INTRODUCTION
Bacteria are the simplest, the smallest and the most successful
prokaryotic microorganisms. Bacteria were among the first life forms
to appear on Earth. The study of bacteria is known as bacteriology a
branch of microbiology. The existence of microbial world was
unknown until the invention of Microscope at the beginning of 17th
Century, which opened the realm of microorganisms to systematic
scientific exploration.
4.
5. GENERAL CHARACTERISTICS
Cosmopolitan
Microscopic in nature
Size: 0.5-1.0μm
Unicellular
Prokaryotic type of cellular organization
They may be Autotrophic, Heterotrophic,
Saprophytic.
Cell wall is made up of Peptidoglycan.
All cell organelles are absent(except Ribosomes)
6. Chlorophyll pigments, if present, are located within
involuted cytoplasmic membranes.
Mesosomes are present
Ribosomes are abundant (70S)
Binary fission is the common method of multiplication
True sexual reproduction is absent
Motile Bacteria may possess one or more flagella.
7. CLASSIFICATION
According to Bergey’s Manual of Systematic Bacteriology, 2nd Edition
Eubacteria is divided into 23 Phyla
Volume-I covers Deeply branching bacterial groups and Phototrophes
Volume-II covers Proteobacteria
Volume-III covers The Low G+C Gram Positive Bacteria
Volume-IV covers The High G+C Gram Positive Bacteria
Volume-V covers Planctomycetes, Spirochaetes, Fibrobacters,
Bacteriodetes & Fusobacteria
8.
9.
10. Exists everywhere….!!!!!!!
Apart from normal Environmental conditions…..
Occur in atmosphere to an height of about 6 KM & on the sea
floor 5 KM below the mean sea level
Exist in Hot springs
Can survive below Freezing point of water
Tolerate to pH range from 0-11
Can tolerate Pressure of 3000-6000 atm
Exist as Free living, Parasitic, Symbiotic
13. CELL WALL
Cell wall is made up of Peptidoglycan or mucopeptide.
Thickness varies from 50-100 A°
Function is purely Mechanical
On the basis of cell wall character and Staining technique Bacteria’s are classified into
a) Gram Positive Bacteria.
b) Gram Negative Bacteria.
14. SURFACE APPENDAGES
FLAGELLA:
May be many times longer than the bacterial cell.
It is a hollow cylindrical strand, made up of protein ‘flagellin’
Consists of 3 morphological parts-basal body, hook & filament
Based on the number & arrangement of flagella, bacteria are classified into
1) Atrichous (Lactobacillus)
2) Monotrichous (Vibrio)
3) Cephalotrichous (Pseudomonas spp)
4) Lophotrichous (Spirillum volutans)
5) Amphitrichous (Nitrosomonas)
6) Peritrichous (Salmonella)
Flagella
15. Pili: long & sparse, rigid & tubular-made up of special protein called
‘Pilin’
used for cell to cell or cell to surface attachment
Spinae: Rigid & tubular appendages found in some Gram Positive
bacteria.
Formed of a single molecule of protein ’Spinin’
Helps the bacterium to resist Salinity, pH. temperature etc.
PILIFIMBRIAE
26. Useful activities.
1. Increases soil fertility through Ammonification,
Nitrification & Nitrogen fixing process.
2. Used in Dairy industries
3. Degradation of Petroleum Hydrocarbons
4. Used in Retting process
5. Decomposition of Dead organisms
6. Insect control
7. Used in Biotechnology for production of various
useful products.
8. To control the Pollution.
27. CONCLUSION
Bacteria are the smallest living organism s on the Earth. Though
having Prokaryotic cellular organization, they show a greater success
in survival than any other living organism . We must give credit to
Antony van Leeuwenhoek for his discovery which opened the
doors of scientific exploration in microbial world. Through their
activities Humans are getting many benefits Economically