Bacteria are single-celled microorganisms that come in a variety of shapes and live in many environments. They were first observed by Van Leeuwenhoek in 1676 and named by Ehrenberg in 1828. Bacteria are prokaryotic, lacking organelles like nuclei, and reproduce through binary fission. There are four main types - rod-shaped bacilli like E. coli, spherical cocci like streptococci, spiral-shaped spirilla, and comma-shaped vibrios like V. cholerae. Bacteria can be helpful by increasing soil fertility, aiding digestion, and creating antibiotics, but can also be harmful as pathogens causing diseases or by contaminating food.

1. Suresh Chaudhary
Department of Science THSS
Bacteria

2. Bacteria
• single-celled microorganism display a wide range of
metabolic types, geometric shapes and
environmental habitats and niches of occurrence.
• Normally only several micrometers in length, bacteria
assume the form of spheres, rods, spirals and other
shapes.
• can live within soil, in the ocean and inside the
human gut
• Anton Van Leeuwenhoek in 1676 AD and term
Bacteria coined by CG Ehrenberg in 1828 AD.

3. Features of Bacteria
o Prokaryotic cell
o have Cell wall
o Reproduce by asexually by fission
o Autotrophic and heterotrophic in nature
o Immotile but bacteria like bacilli and spirilla
can move
o Size ranges 0.5-5 micrometer.

4. Types of Bacteria
There are five types of bacteria:-
1) Bacillus or Rod-shaped Bacteria
( eg.Escherichia Coli)
2) Coccus or Spherical-shaped Bacteria
(e.g. Streptococcus)
3) Sipirillum or Spiral-shaped Bacteria
(e.g. Treponema Pallidum )
4) Comma-shaped Bacteria
(e.g.Vibrio Cholera)

5. Bacillus or Rod-shaped Bacteria
• may be present in as a single
rod or in chains
•both non-parasitic and
parasitic pathogenic species
•Many species of Bacillus can
produce copious amounts of
enzymes which are made use
of in different industries like
alpha amylase used in starch
hydrolysis

6. Spherical shapped bacteria or
coccus
 Coccus (plural cocci) is a term used to
describe any bacterium
that has a spherical,
oval , or generally round shape.
 Clusters like a bunch of grapes or
Joined end to end to form chain or pair
 Cocci bacteria, Streptococci

7. Spiral shapped bacteria
 May have one or more flagella at
their body
 typically lives as individual cells,
instead of being associated in
clusters or chains
 most members of which live in
water with a large amount of organic matter
 Leptospira, Spirillum

8. Comma shaped bacteria
•Are comma shaped
•The body is curved and
has only one flagella
•Typically found in salt
water
•There are over 80 species
of Vibrio bacteria
• eg Vibrio vulnificus,
Vibrio cholera

9. Structure of Bacteria

10. Structure of Bacteria
• lack many of the structures that eukaryotic cells
contain like nucleus
• lack membrane-bound organelles, such as
mitochondria or chloroplasts
• DNA is contained in one circular chromosome, located
in the cytoplasm
• Golgi complex and plastid absent but ribosome present
• may contain flagella -flagella rotate, they spin the
bacteria and propel them forward
• Pili help in attachment to mucosal cell and cojugation

11. Useful Affects of Bacteria
• increase fertility of soil like Rhizobium,
Nitrobacter, Nitrosomonas
• decompose the dead organic materials
• may used as making antibiotic medicine
Bacillus amyloliquefaciens
• help in digestion of cellulose when they are in
intestine
• may used for making food items

12. Harmful Affects of Bacteria
• Bacteria can make our food contaminated
• cause many serious diseases such as, typhoid
fever, syphilis, cholera, tuberculosis and
foodborne illnesses etc
• spoil the food and cause food poison releasing
toxin
• denitrifying bacteria like Pseudomonas
reduce the fertility of soil