Introduction to microbiology, Brief History of Microbiology, Structure of Bacteria, Size and Shape of Bacteria,Bacterial Cell wall, Difference between Gram positive and Gram negative, Fungi , Classification of fungi, Structure and Characteristics of fungi, , Algae, Types of Algae, Protozoan, Virus, virion, Examples of virus

1. Introduction to Microbiology
Bacteria, Fungi, Algae, Protozoan, Viruses

2. Microbiology
 The study of microorganisms is called microbiology,
a subject that began with Anton van Leeuwenhoek’s
discovery of microorganisms in 1675, using a
microscope of his own design.
 They include bacteria, fungi, algae, and protozoa;
microscopic plants (green algae); and animals such
as rotifers and planarians. Some microbiologists also
include viruses, but others consider these as
nonliving.

3. Structure of bacteria; Size
 Bacteria range in size from 0.1 to 600 micro meter.
 The smallest (Mycoplasma) are about 100 to 200 nm
while the largest (E.coli), bacillus shaped, has an
average size of 1.1 to 1.5 wide by 2.0 to 6.0 micro
meter long.
 Some spirochetes occasionally reach 500 micro
meter in length while staphylococci and streptococci
are 0.75 to 1.25 micro meter in diameter.

4. Structure of bacteria; Shape
 Bacteria are classified into these categories;
 Cocci : Spherical or oval shaped
 Staphylococcus, streptococcus, Diplococcus pneumoniae
 Bacilli : Rod Shaped
 Escherichia coli, Bacillus subtilis, Pseudomonas
 Spiral : Spirally coiled
 Spirochete
 Comma
 Vibrio Cholera

5. Bacterial Cell Wall Structure
 Cell Wall
 Cell wall is only absent in Mycoplasma.
 On the basis of Cell wall structural composition, bacteria
can be divided into two groups;
 Gram positive
 Gram negative

6. Characteristics Gram Positive Gram Negative
Chemical Make up Peptidoglycan (50% of dry
weight in some bacterial cell)
Techoic acid
Lipotechoic acid
Lipids (1-4%)
Peptidoglycan (10% of dry weight)
Lipoproteins
Lipopolysaccharides
Lipids (11-12%)
Thickness 20-80 nm 8-11 nm
Outer membrane No Yes
Periplasmic space Present in some Present in all
Permeability More permeable Less permeable
Stain Retention Retain the crystal violet stain
during gram staining
Retain safranin stain during gram
staining
Appearance under
microscope
Appear in purple color under the
microscope by staining
Give red to pink colour under the
microscope by staining
Basal Body of flagellum Two rings Four rings
Pilli No pilli Pilli are present
Examples Lactobacillus, Actinomyces,
Bacillus, Clostridium,
Corynebacterium,
Staphylococci, and
Streptococci
Acetobacter, Chlamydia, Borrelia,
Bortadella, Burkholderia,
Enterobacter, Escherichia,
Helicobacter, Klebsiella and
Neisseria

7. Fungi
 They are eukaryotic; cells contain membrane bound cell organelles including
nuclei, mitochondria, golgi apparatus, endoplasmic reticulum, lysosomes etc.
 They also exhibit mitosis.
 Have ergosterols in their membranes and possesses 80S ribosomes.
 Have a rigid cell wall and are therefore non-motile, a feature that separates
them from animals. All fungi possess cell wall made of chitin.
 Are chemoheterotrophs (require organic compounds for both carbon and
energy sources) and fungi lack chlorophyll and are therefore not autotrophic.
 Fungi are osmotrophic; they obtain their nutrients by absorption.
 They obtain nutrients as saprophytes (live off of decaying matter) or as
parasites (live off of living matter).
 All fungi require water and oxygen and there are no obligate anaerobes.
 Typically reproduce asexually and/or sexually by producing spores.
 They grow either reproductively by budding or non-reproductively by hyphal
tip elongation.
 Food storage is generally in the form of lipids and glycogen.

8. Classification of Fungi ; on the basis of
sexual reproduction
 Zygomycetes: which produce through production of
zygospores.
 Ascomycetes: which produce endogenous spores
called ascospores in cells called asci.
 Basidiomycetes: which produce exogenous spores
called basidiospores in cells called basidia.
 Deuteromycetes (Fungi imperfecti): fungi that are not
known to produce any sexual spores (ascospores or
basidiospores). This is a heterogeneous group of
fungi where no sexual reproduction has yet been
demonstrated.

9. Classification of Fungi ; Based on
Morphology
 Moulds (Molds): Filamentous fungi
 E.g: Aspergillus sps, Trichophyton rubrum
 Yeasts: Single celled cells that buds
 E.g: Cryptococcus neoformans, Saccharomyces cerviciae
 Yeast like: Similar to yeasts but produce pseudohyphae
 E.g: Candida albicans
 Dimorphic: Fungi existing in two different morphological
forms at two different environmental conditions. They
exist as yeasts in tissue and in vitro at 37o C and as
moulds in their natural habitat and in vitro at room
temperature.
 E.g. Histoplasma capsulatum, Blastomyces dermatidis,
Paracoccidiodes brasiliensis, Coccidioides immitis

10. Morphology of fungi:
 Fungi exist in two fundamental forms;
 the filamentous (hyphal)
 single celled budding forms (yeast).
 They have rigid cell wall composed of chitin.
 Some fungi such as Cryptococcus and yeast form of
Histoplasma capsulatum possess polysaccharide
capsules that help them to evade phagocytosis.

11. Algae
 Their DNA is enclosed within a nuclear membrane,
forming the nucleus.
 Algae are eukaryotes and, like plants, contain the
green pigment chlorophyll, carry out photosynthesis,
and have rigid cell walls.
 These eukaryotes may be unicellular and
microscopic in size or multicellular and up to 120
metres (nearly 400 feet) in length.
 Single-celled species may be spherical, rod-shaped,
club-shaped, or spindle-shaped. Some are motile.

12. Types of Algae
 There are a number of types of which some of them
are listed below-
 Blue-green Algae- It is also called as Cyanobacteria.
This type of bacteria is found in lichens, Anthoceros
etc.
 Red Algae- It is also called as Rhodophyta.
 Green Algae; the example of green algae is
Paramecium, hydra and etc.

13. Protozoan
 Single-celled, eukaryotic microorganisms
 Some protozoa are oval or spherical, others
elongated.
 Still others have different shapes at different stages
of the life cycle.
 Cells can be as small as 1 μm in diameter and as
large as 2,000 μm, or 2 mm.
 protozoa lack cell walls
 Able to move at some stage of their life cycle, and
ingest particles of food.
 Some can swim through water by the beating action
of short, hairlike appendages (cilia) or flagella.

14.  Examples of Protozoan
 Amoebas
 Pseudopod
 Apicomplexa

15. Viruses
 All viruses are obligate parasites;
 that is, they lack metabolic machinery of their own to
generate energy or to synthesize proteins, so they
depend on host cells to carry out these vital functions.
 viruses have an extracellular form that carries the
viral nucleic acid from one host cell to another
 In this infectious form, viruses are simply a central core of
nucleic acid surrounded by a protein coat called a capsid.
 The capsid protects the genes outside the host cell; it also
serves as a vehicle for entry into another host cell
because it binds to receptors on cell surfaces.
 The structurally mature, infectious viral particle is called
a virion.

16.  Virion
 an entire virus particle, consisting of an outer protein shell
called a capsid and an inner core of nucleic acid (either
ribonucleic or deoxyribonucleic acid—RNA or DNA).
 The core confers infectivity, and the capsid provides
specificity to the virus.
 Virions generally range in size from 20 to 300
nanometres.
 visible only by electron microscopy

17.  Examples of viruses;
 Rhabdovirus ; that causes rabies
 Rubella virus
 Dengue Virus
 Chickengunya