Microbes are tiny living organisms too small to be seen with the naked eye. They include bacteria, viruses, fungi, protozoa, and algae. Bacteria are single-celled microbes that can be spherical (cocci), rod-shaped (bacilli), or spiral (spirochetes). Bacterial cells contain a cell wall, cytoplasm, DNA, ribosomes, and may have structures like flagella, pili, or a capsule. Flagella and pili help bacteria move and attach to surfaces. Bacteria are classified by their shape, size, and oxygen requirements. The human body contains many beneficial microbes as well as pathogens.

1. Bsc nursing 1 year
Microbiology
Unit :- 2 ( microbes)
BY :- PRAGYA TIWARI

2. Microbes:-
Microbes are tiny living things that are found all around us and are too small to be
seen by the naked eye. They live in water, soil, and in the air. The human body is
home to millions of these microbes too, also called microorganisms.
Some microbes make us sick, others are important for our health. The most
common types are bacteria, viruses and fungi. There are also microbes called
protozoa. These are tiny living things that are responsible for diseases

3. Classification of microbes :-
Microorganisms are categorized into four
major groups:
1.Bacteria:- These are microscopic, single-
celled organisms that grow in diverse
environments. These organisms can live in
soil, the ocean, and also in the human gut.
2.Virus :- A virus is an infectious microbe
consisting of a segment of nucleic acid
(either DNA or RNA) surrounded by a
protein coat. Viruses invade healthy cells and
start to multiply from these cells. A virus can’t
reproduce without these host cells.

4. 3.Algae:- These are simple, non-
flowering, and typically aquatic plants
of a huge group that have seaweeds
and many single-celled forms
in them. Algae has chlorophyll in it
lacks true stems, roots, leaves, and
vascular tissue. Algology or
is the study of algae
4.Fungi: These are a group of
microorganisms that are eukaryotic in
nature and these consist of
microorganisms such as yeasts,
moulds and mushrooms.

5. 5.Protozoa: Protozoa (also protozoan, plural
protozoans) is an informal term for single-celled
eukaryotes, either free-living or parasitic, which feed
organic matter such as other microorganisms or
organic tissues and debris.

6. Bacterial morphology :-
 Morphology describes bacterial shape and size, arrangement and it’s structure.
 There shape can we spherical (cocci), Rod shaped (bacilli) or in helical curve (spiral).
 Some microbes are various shaped called pleomorphic.
According to shape of bacteria :-
1.cocci :- it derived from kokkos means berry. They are spherical in shaped.
1. Staphylococcus :- cocci in cluster.
2. Streptococcus :- cocci in chain.
3. Diplococci :- cocci in pair.
4. Tetrad :- cocci in group of four.
5. Sarcina :- cocci in group of eight.

7. 2.Bacilli :- it derived from word bacules means rod cylindrical and rod shaoed organisms a re called
bacilli following are :-
1. Coccobacilli :- is some of organism length may approximately the width of the organism. These
called coccobacilli.
2. Corynebacteria :- Chinese letter arrangement is seen in corynebacteria.
3. Vibrio :- these are comma shaped, curved rod and derived the name from there characteristics
vibratory motality.
4. Spirochaetes :- it derived from word speria means coil , they are Relativility long, thin, flexible
organism having several coils.
5. Actinomycetes :- it derived from word actis-ray mykes fungus. They ate branching filaments
bacteria.
6. Mycoplasma :- there organism which lack cell wall and do not cause a stable morphology, they
have round and oval body.

8. According to size of bacteria :-
1. Higher bacteria :- they are branching bacteria like :- actinomycetes
2. Lower bacteria :- single small bacteria eg :- cocci, bacilli, vibro.
According to oxygen requirement :-
1. Aerobic :- Required oxygen to grow.
2. Anarobic :- do not required oxygen to grow
3. Facultative :- they grow under both aerobic and anarobic conditions.

9. Bacterial cell :-
Like other living cells
bacteria possess
cytoplasmic
members, cell wall,
ribosomes etc. The
special structure they
may possess are
capsule, flagella,
Fimbriae and pili.
Which are present
outside the cell wall.

10. 1.Cell wall :-
 It is given shape to the bacilli.
 It is touch and rigid structure surrounding the bacteria like a shell.
 Cell wall possess bacterial antigen which are important an virulence and immunity.
 It is elastic and pores.
Function:-
1. Give shape to the cell.
2. Role in division of bacteria.
3. Provide attachment.
4. Protection of internal structure.
5. Offer resistance to harmful effects of environment.
6. Confers rigidity.

11. 2.Cytoplasmic members :-
 It is elastic semipermeable membrane and mainly Lipoprotein in nature and like
beneath cell wall separating it from the cell Semiplasma.
 It control the inflow and outflow of water , nutrients and waste products in or out.
 It can be demonstrate by electron microscope only
 Protoplasma =cytoplasm + nucleus + Other organelle.
Function :-
1. Presence in the membrane of specific enzymes which used in possess through
membrane selective nutrients.
2. It hepls in DNA replication.
3. It provide little Machnical strength to bacterial cell.

12. 3.Cytoplasm :-
 It is watery viscous solution of various organic and inorganic solutes containing
DNA , ribosomes, Mesosomes, and Vacuoles.
 It can be stain by basic dye.
Function:-
They are site of respiratory enzymes in bacteria co-ordinate Nuclear and cytoplasmic
division during binary fission. Responsible for compartmenting DNA at sporulation.

13. 4.Slime layer :-
 Some bacteria secrete viscid
substance, which may diffuse
out into surrounding media
remain outside cell wall.
 This viscid carbohydrate
material called slime layer
Function:-
1. main function is to protect
the bacteria from
environmental dangerous
such as antibiotics.

14. 5.Capsule :-
 It is gelatinous secretion of bacteria. Which get organized as a thick coat around cell
wall, it is known as capsule. The capsule of most bacteria consists of a polysaccharides.
 Development of capsule is depends on the existence of favorable environmental
conditions, such as presence of high sugar concentration and blood serum.
Function :-
1. Attachment to surface.
2. Protection against Phagocytosis Engulfment killing or digestion.
3. Reserve of nutrients and protection against dedication. ( complete drying) .

15. 6.Nucleus :-
 The nucleus contains the thin
fibre of double standard DNA
helix tightly coiled inside the
cytoplasm.
 It does not have Nucleolus.
(Nucleoli are small bodies often
seen within the nucleus.)
 The nucleus is the site for the
genetics transcription.
(Transcription is the process of
copying a segment of DNA into
RNA.)

16. Function :-
1. The main function is to govern gene expression, And facilitate DNA replication
during cell cycle.
2. control of the protein and enzyme synthesis.
3. Control of cell division and cell growth.
4. Storage of DNA, RNA and ribosomes.

17. 7.Plasmid :-
 Some prokaryotes also carry smaller circles of DNA called plasmids.
 Plasmids are the extra chromosomal structures in the cells of bacteria which have the ability to self
replicate.
Function :-
1. They are genetically modified and are used in the recombinant DNA technology.(Recombinant DNA
technology comprises altering genetic material outside an organism to obtain enhanced and desired
characteristics in living organisms or as their products).

18. 8.Mesosomes :-
 It is convoluted (complex) and Multilaminated structure produced by complex cover of the plasma
membrane seen in maany but not all bacteria. And are present in the cytoplasm and remain
attached with the cytoplasmic membrane (plsma membrane).
Function :-
1. It is concerned with respiration, cell division and sporulation, DNA replication etc.

19. 9.Ribosomes:-
 There are two types of ribosomes, free and fixed.
 Free ribosomes are located in the cytosol and are able to
move throughout the cell, whereas fixed ribosomes are
attached to the rER.
 Eukaryotic ribosomes are called 80S ribosomes while
prokaryotes such as bacteria have a smaller version called
70S ribosomes.
Function :-
1. it is the site of protein synthesis in the cell.
2. The ribosome reads the messenger RNA (mRNA)
sequence and translates that genetic code into a specified
string of amino acids, which grow into long chains that
fold to form proteins.

20. 10.Flagella:-
 These are Filamentous, cytoplasmic appendages (attachment) protruding through cell
waal which act as a organ of locomotion (ability to move from one place to another.)
 These are unbranched, long thread like structure composed of entirely of protein.
 It is 0.02 micrometer thick, and it is several times in length of the bacterial cell.
 The flagella are present in all motile bacteria, excepting spirochaetes.
 Their no. Varies upto 10-20/cell depending on bacterial species.

21. According to the arrangement and
distribution of flagella are following types
:-
1. Atrichous :- without flagella.
2. Monotrichous:- single polar flagella.
3. Amphitrichous:- single flagella attached
to each ends.
4. Lophotrichous:- multiple flagella located
at the same spot on the bacteria’s
surfaces.
5. Peritrichous:- numerous flagella all over
the bacterial cell.

22. 11.Pili/fimbriae:-
 These are Filamentous, short, thin, straight, hair like
appendage 0.1to 1.5 u long and less than 4-8 nm
thick.
 They are also called pili.
 Each bacteria may have 100-500 fimbriae
Peritrichously all over teh body of thr bacteria.
 They are made up of protein.
Function :-
1. The primary function of pili are to attached a
bacterial cell to specific surface to other cells
2. Pili can also attachment between bacterial cell.