Important notes (Microbiology)

 

Discoveries, Invention and Contribution in Microbiology

Name	CONTRIBUTION  /   KNOWN AS
Varo and Columella	Postulated that diseases were caused by invisible beings (Animalia minuta) inhaled or ingested..
Robert Hooke	First use a lens to observe “cells.”
Anton van Leeuwenhoek	Invented microscope
Louis Pasteur	Father of microbiology -    Described Fermentation -    Developed germ theory of disease -    Developed pasteurization technique
John Tyndall	Tyndallisation
Robert Koch	Father of bacteriology -    Isolated anthrax bacillus -    discovered Mycobacterium tuberculosis (Koch's bacilli) -    Discovered Cholera bacilli -    Developed KOCH'S Postulate about the germ theory of disease -    Developed petridish and agar for bacterial culture
Sambhu Nath De	Discovered cholera toxin
Richard Petri	Developed the Petri dish (plate)
Lord Joseph Lister (1827-1912)	Father of Antiseptic surgery
Edward Jenner (1749-1823)	Father of immunology
Elie Metchnikoff (1845-1916	Phagocytic theory of immunology
Emil von Behring (1854 -1917) and Shibasaburo Kitasato (1852-1931)	Discovered tetanus (lock jaw) antitoxin
Paul Ehrlich (1854-1915)	·   AFB Staining ·   Found that the dye Trypan Red was active against the trypanosome that causes African sleeping sickness. This dye with antimicrobial activity was referred to as a ‘magic bullet’.
Gerhard Domagk	Nobel prize in 1939 for the discovery of the first sulpha drug.
Alexander Fleming	Discovered the first antibiotic penicillin.
Waksman	Discovery of Streptomycin
Barbara Mclintock	Jumping Genes
Ivanosky	Father of virology
Bersin and Yallow	Radioimmuno assay
Schaudinn and Hoffman	Discovered Spirochaetes
Ronald Ross	Malaria cycle in Mosquito
Christian Gram	Gram stain

Microscope:

S.N.	Microscope type	Resolution	Maximum Magnification	Purpose
1	Light microscope	0.2 micrometer Human eye - 0.1mm	1000-1500 X	All general purpose
2	Electron microscope:-	0.2 nano meter	> 1 lakh times	For studying viruses, the internal structures of cells
3	Phase contrast	Same as light microscope	Same as light microscope	Best for observing live, unstained cells
4	Dark field microscope			For live motile organisms e.g. spirochaetes, protozoa etc
5	Inverted/Stereo Microscope			For observation of cell lines, dissection,
6	Fluorescent Microscope			-   Auramin stain for TB -   Acridine orange stain for Malaria -   Other fluorescent immunological tests

Structure of a Bacteria 

1.                1. Cell Wall: acts as an antigen, provide protection and rigidity

a.       L- form: Mycoplasma species have no cell wall

b.       Spheroplast: Gram Positive bacteria which has lost its cell wall due to antibiotic

2.        Cell membrane: serve as a barrier through which materials enter and exit the cell

3.        Capsule: acts as an antigen, has feeding importance, sticking features and cause disease

4.            4. Mesosome: Respiratory unit

5.        Fimbriae: helps in motility, jerky movement, has sticking feature and acts as an antigen

6.        Pilus: helps in reproduction(conjugation)

7.                 7. Ribosomes: protein formation

8.              8. Nucleoid: transcription and translation

9.           9. Chromosomes: hereditary material

10.         10. Droplets: helpful in storage

11.     Flagella: act as an antigen and helps in motility

12.     Plasmid: has special features of resistance and infection

13.     Fimbriae: Made up of fimbrine protein and range hundreds in number.

14.     Capsule: Slimy layer outside the cell wall usually composed of polysaccharides

Difference between prokaryotes and eukaryotes

Parameter	Prokaryotic Cell	Eukaryotic cell
Size	0.1- 5.0 um	5-100 um
Nucleus	absent	present
Membrane-bound nucleus	absent.	present.
chromosome	One,  circular, coiled	More than one
Cells	Unicellular	Multicellular
Lysosomes and Peroxisomes	absent	present
Microtubules	absent	present
Endoplasmic reticulum	absent	present
Mitochondria	absent	present
Cytoskeleton	absent	present
Ribosomes	70's	80's
Vesicles	present	present
Golgi apparatus	absent	present
Vacuoles	absent	present
Sexual reproduction	absent	present
Endocytosis and exocytosis	absent	absent
Pili and fimbriae	Present	Absent
Transcription	Occurs in the cytoplasm	Occurs inside the nucleus.

Difference between prokaryotic and eukaryotic cell

S.N.	Character	Gram-Positive Bacteria	Gram-Negative Bacteria
1.	Gram Reaction	Retain crystal violet dye and stain blue or purple on Gram’s staining.	Accept safranin after decolorization and stain pink or red on Gram’s staining.
2.	Cell wall thickness	Thick (20-80 nm)	Thin (8-10 nm)
3.	Peptidoglycan Layer	Thick (multilayered)	Thin (single-layered)
4.	Rigidity and Elasticity	Rigid and less elastic	Less rigid and more elastic
5.	Variety of amino acid in cell wall	Few	Several
6.	Aromatic and Sulfur-containing amino acid in cell wall	Absent	Present
7.	Periplasmic Space	Absent	Present
8.	Teichoic Acids	Mostly present	Absent
9.	Porins	Absent	Present
10.	Lipopolysaccharide (LPS) Content	Virtually None	High
11.	Lipid and Lipoprotein Content	Low (acid-fast bacteria have lipids linked to peptidoglycan)	High
12.	Mesosomes	Present	Absent
13.	Flagellar Structure	2 rings in basal body	4 rings in basal body
14.	Morphology	Usually cocci or spore-forming rods (exception: Lactobacillus and Corynebacterium)	Usually non-spore-forming rods (Exception: Neisseria)
15.	Endospore formation	Some produce endospores during unfavorable conditions.	Usually not found to produce endospores.
16.	Toxin Produced	Exotoxins	Endotoxins or Exotoxins
17.	Pathogens	Few pathogenic bacteria belong to the Gram-positive group.	Most pathogens are Gram-negative.
18.	Nutritional Requirements	Relatively Complex	Relatively Simple
19.	Resistance to Physical Disruption	High	Low
20.	Cell Wall Disruption by Lysozyme	High	Low (requires pretreatment to destabilize outer membrane)
21.	Susceptibility to Penicillin and Sulfonamide	High	Low
22.	Susceptibility to Streptomycin, Chloramphenicol, and Tetracycline	Low	High
23.	Inhibition by Basic Dyes	High	Low
24.	Susceptibility to Anionic Detergents	High	Low
25.	Resistance to Sodium Azide	High	Low
26.	Resistance to Drying	High	Low
27.	Examples	Staphylococcus Streptococcus Bacillus Clostridium Enterococcus Listeria	Escherichia Salmonella Klebsiella Proteus Helicobacter Pseudomonas

Some important notes 

 

Gram Stain Limitations

These Microbes May Lack Real Color 

-          Treponema (too thin to be visualized)

-          Mycobacteria (high lipid content in cell wall, detected by carbolfuchsin in acid fast stain) 

-          Mycoplasma (no cell wall) 

-          Legionella pneumophilia (primarily intracellular) 

-          Rickettsia (intracellular) 

-          Chlamydia (intracellular and lacks muramic acid in cell wall)

Encapsulated bacteria

SHiNE SKlS

-           Streptococcus pneumoniae (Group A)

-          Haemophilus influenzae type B

-          Nesseria meningitides

-          Eschiria coli 

-          Salmonella 

-          Klebsiella pneumoniae 

-          S treptococcus agalacticae ( Grou p B)

PiPigment-producing bacteria

·         Actinomyces israelii -- yellow "sulfur" granules (Israel has yellow sand and the explosions make it smell like sulfur)

·         S. aureus -- yellow pigment (aureus means gold)

·         Pseudomonas aeruginosa (Aeurgula is green)

·         Serratia marcenscens -- red pigment (red maraschino cherries)

 

Enteriobactericiae at a glance