Bacteria are the simplest and smallest prokaryotic microorganisms. They are ubiquitous, existing everywhere from atmospheric heights of 6km to ocean depths of 5km. Bacteria exhibit a wide range of shapes and many are motile with flagella or pili. They reproduce asexually through binary fission and lack true sexual reproduction. Bacteria play important economic roles through causing diseases, food spoilage, increasing soil fertility through nitrogen fixation, and use in biotechnology and pollution control.

1. Manjunatha S
I M.Sc.(Botany)
University of Mysore
EUBACTERIA
AN OVERVIEW

2. CONTENTS
• Introduction
• General characteristics
• Classification
• Distribution
• Shapes
• Cellular organization
• Flagella
• Bacterial growth
• Nutrition
• Reproduction
• Economic importance
• Conclusion
• Reference

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.

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

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

11. SHAPES OF EUBACTERIA

12. CELLULAR ORGANIZATION

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

16. Bacterial growth
Involves 4 stages
1. Lag phase
2. Exponential phase
3. Stationary phase
4. Death phase

17. Autotrophic
bacteria
Photosynthetic
Bacteria
Green sulphur
Bacteria
Chlorobium,
Clathochloris
Purple Sulphur
Bacteria
Thiospirillum,
Chromatium,Amoebobact
er
Purple non-Sulphur
Bacteria
Magnetospirillum
Azatospirillum
Cyano Bacteria
Nostoc,
Anabaena
Chemosynthetic
Bacteria
Sulphur
Bacteria
Thiobacillus
Beggiatoa
Iron
Bacteria
Ferrobacillus,
Gallionella
Hydrogen
Bacteria
Pseudomonas
spp
Nitrifying
Bacteria Nitrosomonas
Nutrition

18. Heterotrophic
Bacteria
Parasitic Bacteria
Salmonella,
Pneumococci
Saprophytic
Bacteria Lactobacillus
Symbiotic Bacteria Rhizobium

19. REPRODUCTION
Asexual reproduction
1. Binary Fission
2. Budding
3. Conidia
4. Cysts & Endospores
True sexual reproduction is absent, But sexuality is accomplished by
interchange of genetic material.
1. Conjugation
2. Transformation
3. Transduction

20. Binary Fission Budding & Conidia

21. Cysts Endospore

22. Transformation

23. Transduction

24. Conjugation

25. ECONOMIC IMPORTANCE
Harmful activities
1. Causes many diseases
Plants
Ring spot of Potato --- Xanthomonas solanacearum
Citrus canker --- Xanthomonas citri
Soft rot of Mango --- Bacterium cartovorus
Tundu of Wheat --- Corynebacterium tritici
Blight of Bean --- Pseudomonas phaseolicola
Animals
Plague --- Yersinia pestis
Cholera --- Vibrio cholerae
Tuberculosis --- Mycobacterium tuberculosis
Typhoid --- Salmonella typhi
Gastro-enteritis --- Escherichia coli
2. Food spoilage
3. Denitrification by Bacillus licheniformis, Pseudomonas aeruginosa.

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

28. REFERENCES
• Prescott−Harley−Klein, Microbiology, 5th Edition
The McGraw−Hill Companies, 2002
• Singh Pande Jain, Textbook of Botany, 4th Edition,
Rastogi Publications, Meerut 2011
• www.googleimages.com

29. THANK YOU