HISTORY AND SCOPE OF MICROBIOLOGY

AN INTRODUCTION TO MICROBIOLOGY

Youngest biological sciences
Started in middle of nineteenth century- Mendelian genetic & natural selection
Microbiology now stands with older biological science that is zoology and botany
Microbiology is the study of microscopic forms of life concerned with microorganism structure, function, nutrition, reproduction, heredity, chemical activities, classification, identification.

MICROBES

Not readily visible with naked eyes
Every living organism are dependent on microorganism directly or indirectly
Microorganism are single and multicellular organisms that donot include tissue specialization
Groups of microorganism includes- bacteria, cyanobacteria, algae, fungi(mould & yeast), protozoa, nematodes, viruses and some viroids and prions.
Microorganism are present in all environment
From human beings they are parts of our world.
Have beneficial influence in our daily life.
Breads-made of yeast- that ferment sugar and carbonate the dough before baked.
Cheese,yogurt,sour cream require microorganism.
As a fertilizer in plants or microorganism reduced nitrogen for plant growth
Antibiotics for bacteria disease(Strep throat,pneumonias,gonorrhea,syphilis)
Used as vaccine– tetanus,diphtheria,whooping cough,measles & mumps
Microbes plays important part in waste disposal.
Recycling essential nutrient •Microbes produces- organic acid,solvent and enzyme

Produces amino acid, vitamins, growth factors, therapeutic enzymes for curing malnutrition and health problem of human being.

Roles of extraction of metals from ores
As a fuel(by using agriculture waste and extreta)- biogas,gasohol
Genetic engineering technology- produce new form organisms by inserting specific pieces of foreign materials(genes)
Microorganism is directed to produce protein such as
Hormones- insulin(treatment of diabetes), •tissue plasminogen activator(TPA- treatment of heart attack victim),
Antiviral agent-inteferons(treatment of cancers and disease caused by virus),
Human growth factors(increase bone growth),
Amino acids
As a food spoilage agent
Human disease — Acquired Immune Deficiency Syndrome(AIDS),herpes,legionnaires disease,influenza,Tuberculosis,typhoid,dermatomycoses,dysentery,malaria.
Animal disease – Burucellosis,tularemia
Plant disease – Mildews,rusts,smuts,cankers,leaf spoils etc

French scientist Louis Pasteur expressed- The role of infinitely small is infinitely large.He was first scientist to recognize biological function of microbes.

Microbiology: A multifaceted Science

It is more than just a taxonomic study of microorganism.
It is also concerned with role of organism in causing disease
Microbiologist study wide range of microscopic form of life and their activity in natural and artificial environment.
Field of microbiology includes the study of bacteria, algae, fungi(mould & yeast), protozoa, virus and subviral agents of disease.
Bacteriology- study of unicellular procaryotic organism known as bacteria.
It deals with the uses of bacteria in industry
Role of bacteria in ecology of world
Bacterial genetics,structure and multiplication
Mechanism by which bacteria cause disease
Bacteriologist is a person who studies bacteriology
Mycology– is a study of fungi,including moulds,mushroom and yeast.
Fungi have a wide variety of sizes,colours,shapes.
Non photosynthetic.
Many live in soil & play important part in decomposition of organic matter.
Produces several kind of food & antibiotics
Causes disease in humans,animals & plants.
Mycologist study about fungi.
Phycology(Algology)- It can be unicellular & multicellular giant kelp(50m or more)
Beautiful colours – brown,green,red and yellow
Photosynthetic.
It increases level of dissolved oxygen in their immediate environment and serve as food sources for humans & livestock.
Phycologist study algae
Protozoology – larger than most other organism
Complex- structure & activities
Found –sewage,water,intestinal tract of insects and damp soil.
Feed on other microorganism and dead organic matter.
Harmless
But few causes disease such as malaria, amoebiasis, sleeping sickness, leishmaniasis etc.
Parasitic animals.
Arthropods of medical importance are subject matter of parasitology.
Protozoologist study protozoa.
Virology – study of noncellular(acellular) organism called viruses.
Structure & reproduction of viruses for studing disease and how to control.
Different multiplication than other organism.
Virus depend on host cell for growth & reproduction.
Obligate intracellular parasites •Microorganism can be infected by cells.
Virologist study virus

INTEGRATIVE APPROACH FOR SUBDIVISION OF MICROBIOLOGY

MICROBIAL ECOLOGY – Study the relation between microorganism & environment
MICROBIAL MORPHOLOGY & CYTOLOGY – Study of shapes and the microscopic & submicroscopic details of microbial cells(ultrastructure).It involve the technique of electron microscopy.
MICROBIAL PHYSIOLOGY – Study of microorganism function. Metabolic activities, effect of environment on microbial synthetic pathways and nutritional requirement of different groups are studied.
MICROBIAL GENETICS – Study of genes, inheritance pattern, genetic exchange between microbes, how genes is expressed within organism, control of cellular activities,effect of mutation(genetic change)
MICROBIAL TAXONOMY – Naming & classification of microorganism on basis of similarities & differences.
MOLECULAR BIOLOGY – Programming genetic system and creation of macromolecules & important biological chemicals in organism. It deals with DNA and protein synthesis in organism
BIOCHEMISTRY – Concerned with chemical basis of living matter and varies metabolites reaction associated with them.
BIOPHYSICS- Principles of physics apply to living organism.

THE POSITION OF MICROORGANISM IN LIVING WORLD

EARLIER LINNAEUS CLASSIFICATION SCHEME( CAROLUS LINNAEUS)

Animals differ from plants as they lack typical structure of plants, such as leaves, stems & roots.
They are active motile, non-photosynthetic and quite complex
Plants are opposite of animals in all these respects.
Until 1830,taxonomic status of most life forms remained fairly constant.
Discovery of wide variety of microorganism presented biologist with several problems.
Some microorganisms presented as either plant or animals, many could not.
Presence of outer structure called cell wall which could define microbial cell as plants.
Animal like cell such as protozoa did not have this structure.
Such cell ingest and capture solid foods but plants cannot.
Thus algae, bacteria, fungi(moulds and yeast) were grouped into plantae and protozoa as animalia.
Some microorganism got the properties of both plant & animals.

THE PROTISTA: THE THIRD KINGDOM

Difficulties were there in applying 2kingdom classification on microorganism.
Microorganism differ widely in metabolic and structural properties.
Some are plant like ,some are animal like & some totally different.
In 1866 Ernst Haekel proposed 3 kingdom to eliminate confusion.
Kingdom was names Protista (Derived from Greek word-primitive or first)
The new kingdom consists single celled microbes such as algae,bacteria,fungi and protozoa and multicellular which was not differentiated or organized into tissue or organ such as higher plant or animals.
It was never universally accepted.

1957- Roger Stanier

They distinguished two subgroups based on cellular characteristics
Lower protist – procaryotes – primitive nucleus- All bacteria eubacteria, cyanobacteria, archaeobacteria, rickettsia, chlamydia, mycoplasma )
Higher protist – Eucaryotes- well defined nucleus- algae, fungi, protozoa
Virus are left out of this scheme.

DIFFERENCE

WHITTAKER’S 5 KINGDOM CONCEPT

2 Kingdom & 3 kingdom is over simplified and many biologist favours dividing organisms among 5 kingdom as first suggested by R.H Whittaker 1969
Organisms are place in 5 kingdoms on basis of atleast 3 major criteria.
Cell type- procaryotes or eucaryotes
Level of organization- solitary and colonial unicellular organization or multicellular
Mode of nutrition
In Whittaker’s system,
Animalia contains- multicellular organism with wall less eucaryotic cell and primarily ingestive nutrition.
Plantae contain- multicellular plants with called eucaryotes and primariliy photoautotrophic nutrition and pinocytosis.

Other 3 kingdom

Monera – procaryotes in Bergey’s manual
Fungi– eucaryotes, multinucleated organism, with nuclei dispersed in a walled and often septate mycelium, nutrition is absorptive
Protista– least homogeneous and difficult to define – eucaryotic with unicellular organization, either in a form of solitary cell or colonies of cell lacking true tissue.
They may have ingestive, absorptive or photoautotrophic nutrition
Includes algae, protozoa and simple fungi

An environmental isolate of Penicillium

WOESE’S THREE KINGDOM SYSTEM

IN 1977 Carl R. Woese proposed a three kingdom of classification.
Grouping of all bacteria into procaryotes in 5 kingdom system is based on microscopic observation
Woese proposal was based on Modern techniques in molecular biology and biochemistry that reveal two types of procaryotics cells
Ribosomes are not same in all procaryotic cell
Comparing sequence of nucleotides in ribosomal RNA(rRNA) from different kind of cells there are 3 distinctly different cell groups,the eucaryotic and 2 different procaryotes – Eubacteria (true bacteria) and Archaeobacteria (ancient)
Woese believed that Archaeobacteria and Eubacteria(Procaryotes in 5 kingdom) having similar appearance should form their own separate branches Evolutionary tree.
All Eucaryotes- protista, Fungi, plant and Animal in Whittaker’s system)should be grouped into third kingdom.
Difference in membrane lipid structure,transfer RNA molecules and sensitivity to antibiotics also support classification of 3 kingdom.

Difference between Archeobacteria and Eubacteria

Archeobacteria- never contain peptidoglycan
Lives in extreme environment
Do all unusual metabolic processes

Archeobacteria includes 3 groups

Methanogens– strict anaerobes- produce methane from carbondioxide
Extreme Halophiles- require high concentration of salt for survival
Thermoacidophiles– grow in hot acidic environment

PROCARYOTES AND EUCARYOTES EVOLUTIONARY RELATIONSHIPS

Mitochondria and chloroplast,two eucaryotic structure are descended from procaryotes.
It become trapped in large cell and established endosymbiosis relation with it.
Mitochondria is though to be actively metabolizing bacteria an Chloroplast as photosynthesizing descent occurred in Eucaryotic cells.
Many portion remain unclear, biochemical and metabolic differences donot support the idea.
With the discovery of archeobacteria, common ancestor of all form of life & evolution of eucaryotic cell become approachable.

TAXONOMIC STRUCTURE OF VIRUSES

Virus have definite property that set them apart from all other life form
Neither procaryotes nor eucaryotes
Virus are not cell
Virus consists of DNA or RNA surrounded by protein coat
After invading living cells,virus use metabolic and genetic machinery of host cell to reproduce.
Virus infect bacteria,algae,protozoa,fungi .
Boundry between living and non living.
They undergo mutation(genetic change)
Have mean of replicating and increase in number
Obligatory intracellular parasites
Virus get incorporated in host cell and resemble host cell.
Origin of Virus hypothesis

Arose from independently replicating strands of nucleic acids(Plasmid)
Developed from degenerative cells through many generation-lost its ability to grow but can grow when associated with living cell