Manjunatha S

I M.Sc.(Botany)

University of Mysore

EUBACTERIA AN OVERVIEW

CONTENTS

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

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.

GENERAL CHARACTERISTICSCosmopolitanMicroscopic in natureSize: 0.5-1.0μmUnicellularProkaryotic type of cellular organizationThey may be Autotrophic, Heterotrophic,

Saprophytic.Cell wall is made up of Peptidoglycan.All cell organelles are absent(except Ribosomes)

Chlorophyll pigments, if present, are located within involuted cytoplasmic membranes.

Mesosomes are presentRibosomes are abundant (70S)Binary fission is the common method of multiplication True sexual reproduction is absentMotile Bacteria may possess one or more flagella.

CLASSIFICATIONAccording to Bergey’s Manual of Systematic Bacteriology, 2nd EditionEubacteria 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

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 levelExist in Hot springsCan survive below Freezing point of waterTolerate to pH range from 0-11 Can tolerate Pressure of 3000-6000 atm Exist as Free living, Parasitic, Symbiotic

SHAPES OF EUBACTERIA

CELLULAR ORGANIZATION

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.

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 & filamentBased on the number & arrangement of flagella, bacteria are classified into1) Atrichous (Lactobacillus)2) Monotrichous (Vibrio) 3) Cephalotrichous (Pseudomonas spp)4) Lophotrichous (Spirillum volutans) 5) Amphitrichous (Nitrosomonas)6) Peritrichous (Salmonella)

Flagella

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

Bacterial growth

Involves 4 stages1. Lag phase2. Exponential phase3. Stationary phase4. Death phase

Autotrophic bacteria

Photosynthetic Bacteria

Green sulphur Bacteria

Chlorobium, Clathochloris

Purple Sulphur Bacteria

Thiospirillum, Chromatium,Amoebobact

er

Purple non-Sulphur Bacteria

MagnetospirillumAzatospirillum

Cyano Bacteria Nostoc, Anabaena

Chemosynthetic Bacteria

Sulphur Bacteria

ThiobacillusBeggiatoa

Iron Bacteria

Ferrobacillus, Gallionella

Hydrogen Bacteria

Pseudomonas spp

Nitrifying Bacteria Nitrosomonas

Nutrition

Heterotrophic Bacteria

Parasitic Bacteria Salmonella, Pneumococci

Saprophytic Bacteria Lactobacillus

Symbiotic Bacteria Rhizobium

REPRODUCTION

Asexual reproduction1. Binary Fission2. Budding3. Conidia4. Cysts & Endospores

True sexual reproduction is absent, But sexuality is accomplished by interchange of genetic material.1. Conjugation2. Transformation3. Transduction

Binary Fission Budding & Conidia

Cysts Endospore

Transformation

Transduction

Conjugation

ECONOMIC IMPORTANCEHarmful activities1. 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 coli2. Food spoilage 3. Denitrification by Bacillus licheniformis, Pseudomonas aeruginosa.

Useful activities.1. Increases soil fertility through Ammonification,

Nitrification & Nitrogen fixing process.2. Used in Dairy industries 3. Degradation of Petroleum Hydrocarbons4. Used in Retting process5. Decomposition of Dead organisms6. Insect control7. Used in Biotechnology for production of various

useful products.8. To control the Pollution.

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

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

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