Bacteria are unicellular prokaryotic organisms that lack a true nucleus, characterized by various shapes such as cocci, bacilli, and spirilla. They can reproduce asexually through binary fission or form endospores to survive unfavorable conditions, and they acquire nutrients either autotrophically or heterotrophically. Some bacteria are motile with flagella, while others are not, and they play significant roles in ecosystems, including causing diseases.

1. BACTERIA IMAGES: EASY DRAWING OF
BACTERIA
Spread the love
BACTERIA IMAGES
INTRODUCTION: Bacteria are the simplest ,most primitive and unicellular organisms without a true nucleus.
That is why they are prokaryotic. they are placed under kingdom Monera. they are found everywhere in
air,water,soil,food,inside our body etc. they lack nucleus and other cell organelles of complex cellslike
plants,they possess a cell wall. each bacterial cell has its nuclear material in the form of a single
chromosome which is not enclosed in a nuclear membrane.
STRUCTURE OF BACTERIA
SIZE:
Bacteria are the smallest of all living organisms. Their size is usually expressed in microns. An
average spherical bacterial cell is 0.5 micrometre (µ) in diameter but most of them range from 0.2 to 2.0
micrometer (µ) in width and less than 2-10 micrometre (µ) in length. Bacillus forms vary from 0.3 to 15
micrometer (µ) in length and from 0.2 2.0 micrometre (µ in width. A single drop liquid may contain about 50
million bacteria.
SHAPE
According to shape bacteria are of four types.
SHAPE OF BACTERIA
SHAPE OF
BACTERIA
SHAPE CHARACTERISTICSDIAGRAM

2. COCCUS
(plural:
cocci)
Spherical
shaped
These may be present
in clusters
(Staphylococci) like a
bunch of grapes.
Sometimes form long
chain(Streptococci)
or in
pairs (Diplococci)
BACILLUS
(plural:
bacilli)
Rod shaped
These may be present
as a single
(Escherichia coli)
or in chains (Bacillus
anthracis)
SPIRILLUM
(plural:
spirilla)
Spiral or
curved
shaped
These bacteria may
have one or more
flagella at the end of
their bodies
(Leptospira spirillum)

3. VIBRIO
Comma
shaped
The body is curved
with only one
flagellum (Vibrio
cholera)
STRUCTURE OF BACTERIUM
*Each bacteria is a simple cell.
*It contains protoplast which is a living substance.
* Bacteria cell is surrounded by a non-living rigid cell wall.
* Bacteria cell wall contains peptidoglycan . It is not cellulose.
*Beneath the cell wall is a thin membrane which surrounds the cytoplasm.
*It does not contain membrane bound organelles like chloroplasts, mitochondria, golgi body and
endoplasmic reticulum.
* The chromatin material is in the form of a single molecule of circular DNA attached to the cell membrane. It
is not enclosed in a nuclear membrane.
* Nucleoid is the single circular DNA molecule which is the genetic material present in the centre of the
cell.
* Some bacteria have a slimy protective layer called capsule outside the cell wall.
*This capsule helps bacteria to remain dormant during unfavourable conditions.
*Ribosomes and plasmid which is the smaller ring of DNA present in the cytoplasm.

4. *Ribosomes help in protein synthesis.
METABOLIC ACTIVITY OF BACTERIA
MOVEMENT: Most bacteria are immotile i.e. cannot move on their own. They are passively transported by
wind , water or simply by contact. Majority of cocci are non-motile. Some Bacteria such as bacilli and spirilla
can move by the lashing movement of whip- like flagella in a liquid or watery medium. Some of them have a
single flagellum at one end, while bacterium like Salmonella have
flagella all over the body.
NUTRITION: Most bacteria do not have chlorophyll. Nutrition in bacteria may be autotrophic or heterotrophic.
NUTRITION IN BACTERIA
TYPE OF NUTRITION SUBDIVISION CHARACTERISTICS
1)Autotrophic nutrition
i) Photosynthetic bacteria
ii)Chemosynthetic bacteria
It contains bacteriochlorophyll
and produces food material
using light energy e.g. green
sulphur bacteria.
This type of bacteria obtain
energy by oxidizing inorganic
compounds e.g. sulphur
bacteria.
2)Heterotrophic nutrition
i)Saprophytic nutrition
ii)Parasitic nutrition
In this type of nutrition bacteria
obtain food from perishable
organic dead and decaying
matter.
In this nutrition bacteria can get
food from other living
organism (HOST)gets shelter
on
the host e.g. Mycobacterium
tuberculosis.
HETEROTROPHIC NUTRITION:
a)Saprophytic nutrition- In this nutrition bacteria obtain food from dead and decaying organisms.
1. b) Parasitic nutrition- In this nutrition bacteria obtain food from other living organisms.
In heterotrophic nutrition bacteria secrete enzymes to make food material soluble which is then absorbed by
the bacterial cell. Most of the heterotrophic bacteria cause diseases to the hosts.
RESPIRATION OF BACTERIA
According to the requirements of oxygen in respiration bacteria may be divided into two types:
1. a) Aerobic bacteria:- They respire by utilising oxygen. By this process glucose is completely oxidised.
2. b) Anaerobic bacteria:- Some bacteria respire in absence of oxygen. We can get many useful products
by utilising anaerobic process.
PRODUCTION OF ENERGY DURING RESPIRATION:

5. Complete oxidation of food molecules during aerobic respiration results in the production of comparatively
more energy (683kcal) and this is happening in aerobic respiration.
Partial breakdown of food molecules during anaerobic respiration results in the production of less energy
(50 kcal ).
REPRODUCTION OF BACTERIA
1. a) Asexual reproduction:- In bacteria reproduction rakes place mostly by asexul processes . It is of
various types.
1. i) Binary fission: It is very much popular among bacteria. Theoretically one fact can be shared that ”
under ideal conditions, some bacteria divide at a rapid rate. A single bacterium cell would produce
281,514,871,750,658 bacteria at the end of 24 hours”. However, it never happens in nature due to
accumulation of toxins in the medium and depletion in food supply.
Binary fission takes place by simple mitotic division. In this process a fully grown bacterial cell divides into
two identical cells by a constriction in the cell wall. The two resulting bacteria get separated and after
reaching maturity redivide. In certain bacteria, the divided cells do not separate but remain attached giving
rise to chains or colonies. During fission, bacteria divide into two. Cell division is preceded by duplication of
the DNA. The bacterium grows and it’s nucleus enlarges due to DNA duplication. The two DNA are pulled
apart to two sides. It is generally happened in favourable conditions.
1. ii) Spore or Endospore formation:- Endospores are formed in a few bacteria. These are thick- walled,
non- motile resistant bodies formed within the cells. These Endospores are resistant to temperature as
low as ice and high as boiling water. They can withstand dry conditions and remain alive in adverse
conditions for a long time. Fortunately only two of the pathogenic bacteria i.e. Tetanus causing and
Anthrax causing bacteria produce Endospores.

6. Spore formation in bacteria is not a method of reproduction but simply a method of escaping unfavorable
conditions as there is no increase in the number of individuals.
Endospore formation is not a method of reproduction by bacteria. It is rather a means to protect themselves
under unfavorable conditions. That time bacteria form thick- walled, non- motile resistant bodies called
Endospores. These are formed within the cells. The cytoplasm of the çell condenses and then secretes a
thick wall to form Endospore. It remains dormant and can tolerate high temperature, freezing temperature,
pH changes, effects of chemicals. On the return of favourable conditions , each Endospore germinate to
form a single bacterial cell.
1. B) SEXUAL REPRODUCTION:- It occurs in bacteria through conjugation. This is an unusual form of
reproduction in bacteria. During conjugation bridges are formed between two cells. Exchange of genetic
material is occurred through the bridge. e.g. Escherichia coli . The new individual divideds and redivides
to form new daughter cells .