Notes for Microbiology

8/22/2019 Notes for Microbiology

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Introductory Microbiology notes for bioprocess engineers

COMMON CHARACTERISTICS OF LIVING THINGS (ORGANISMS):

All biological systems [living things] have the following characteristics in common:

1. The ability to ingest or assimilate nutrients (food substances) and metabolize them for

energy and growth.

2. The ability to excrete waste products.

3. The ability to react to their environment sometimes called irritability.

4. The ability to reproduce its own kind.

5. There is susceptibility to mutation.

Microbiology is a science that deals with the study of living organisms that cannot beseen by the naked eye. These can be seen with the aid of microscopes, which magnifyobjects.

History of development of Microbiology as a science:

Many scientists contributed to the science of microbiology.Louis Pasteur (1822-1895)

Louis Pasteur was a French chemist and a crystallographer. His contribution tomicrobiology is so great that he is considered to be the “Father of Microbiology”.

Contribution to science: As a chemist He was working with tartaric acid crystals. Hecould pick up the dextro and levo rotatory crystals by seeing the morphology of the crystals. Later he was called to solve some of the problems in fermentation industryand turned his attention to biological process of fermentation.Contribution to wine industry1. He discovered that alcohol production from grape juice was due to Yeast.2. He found out that large amounts of lactic acid production was due to the presence or

contamination of rod shaped bacteria.



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3. He observed that the process of alcohol production i.e. FERMENTATION took placein the absence of air(high dissolved oxygen in the medium) .

4. He coined the terms aerobic to describe those organisms requiring air andanaerobic to describe those organisms which do not require air for their growth.

Contribution to modern microbiologyPasteur disproved the theory of spontaneous generation. The theory proposed thatliving organisms originated spontaneously, particularly from decaying organic matter.He disproved it.Pasteur’s swan neck flask Pasteur poured meat infusions into flasks and then drew the top of each flask into along curved neck that would admit air but not dust. He found that if the infusions wereheated, they remained sterile (free from any growth) until they were exposed to dust. Heopened them on a dusty road and resealed them and demonstrated the growth of microorganisms in all the flasks. The unopened flasks were sterile. Thus he disprovedthe theory of spontaneous generation.

Louis Pasteur defined pasteurization to prevent spoilage of food by bacteria, developvaccines and disproved the scientific dogma of “Spontaneous Generation”. He defined“Germ Theory” and demonstrated that germs were responsible for disease.Edward Jenner 1796It was an ancient observation that persons, who had suffered from a specific diseasesuch as small pox or mumps, resisted the infection on subsequent exposures. Theyrarely contracted it second time. Such acquired resistance is specific. Edward Jenner a country doctor in England noted a pustular disease on the hooves of horses called thegrease. This was carried by farm workers to the nipples of cows (cow pox). This wasagain carried by milk maids. They got inflamed spots on the hands and wrists. Thepeople who got this cow pox were protected from small pox. He reported that 16 farmworkers who had recovered from cow pox were resistant to small pox infection.He took the material from the cow pox and inoculated into the cut of an 8 year old boyon 14 May 1796. Two months later Jenner inoculated the same boy with material takenfrom small pox patients. This was a dangerous but accepted procedure of that time andthe procedure was called variolation. The boy was protected against small pox. Hisexposure to the mild disease cow pox had made him immune to the disease small pox.In this manner Jenner began the science of Immunology, the study of the body’sresponse to foreign substances.Robert Koch (1843-1910)Robert Koch was a German physician.1. For the first time he showed the evidence that a specific germ (Anthrax bacillus) was

the cause of a specific disease (splenic fever in sheep)2. He established that a specific germ can cause a specific disease and introduced

scientific approach in Microbiology.3. He discovered Bacillus anthracis (Anthrax bacillus), Mycobacterium tuberculosis, and

Vibrio cholerae.4. He modified Ziehl-Neelsen acid fast staining procedure which was introduced by

Ehrlich.5. He devised the solid medium to grow the microorganism to get single colonies.



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6. He introduced Koch’s thread method to find out the efficacy of disinfectants 7. He established certain rules that must be followed to establish a cause and effect

relationship between a microorganism and a disease. They are known as Koch’sPostulates

8. He also described the Koch’s Phenomenon

The need for Koch’s postulates: In those days there were no perfect techniques toidentify the organisms. Solid media and staining techniques were not available. So theetiological role of organisms was not known. To prove the etiology there were not strictcriteria. So there was a need to establish criteria.

Koch’s Postulates 1. The organism should be regularly seen in the lesions of the disease.2. It should be isolated in pure culture on artificial media.3. Inoculation of this culture should produce a similar disease in experimental

animals.

4. The organism must be recovered from the lesions in these animals.

Postulate 1The organism should be found in lesions of the disease. All the causative agents of thedisease are seen in the particular diseases. If we take pneumococci as example, theyare seen in all the pneumonia cases.Postulate 2It should be isolated and grown in solid media. Pneumococci are grown in solid mediaand are isolated from the diseases. Some organisms do not grow on solid media or thesolid media are not developed yet.

Example: Mycobacterium leprae andTreponema pallidum

Postulate 3The organisms should produce the exact disease in experimental animals

Almost all the pathogenic organisms produce the same disease in experimentalanimals. Usually rats, mice, rabbits or guinea pigs are used as experimental animals.Pneumococci produce pneumonia in animals. Salmonella species do not producetyphoid fever in rat, mice or rabbit. So chimpanzee is taken as experimental animal andit produces fever in chimpanzee.Postulate 4It should be isolated from the diseased animal also

Pneumococci are isolated from the experimental animals also.

Modern addition to Koch’s PostulatesToday we recognize additional criteria of causal relation between a microorganism anda disease.The important one is the demonstration of abnormally high concentration of specificcirculating antibodies to the organism in the infected host Or, the presence of



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abnormally high degree of specific immunity or hypersensitivity to the infecting agent ina recently recovered host.

LimitationsSome organisms have not yet been grown in artificial culture media

Example: Mycobacterium leprae and Treponema pallidum.

Usefulness of Koch’s Postulates 1. It is useful in determining pathogenic organisms2. To differentiate the pathogenic and nonpathogenic microorganism3. For the classification of organisms4. To detect the susceptibility, resistance of the laboratory animals.

ConclusionsKoch has done a valuable work in the field of Microbiology and has made postulates,which have merits, demerits and limitations with modern omission and addition.

Other ‘applied microbiologists’:

Ignaz Semmelweis was the first to recognize the need for good hygiene duringmedical procedures. The first to identify nosocomial infections.

1827-1912 Joseph Lister developed antiseptic methods for use in surgery andmedicine.

1854-1915 Paul Ehrlich developed chemotherapy to cure infectious diseases anddiscovers antibiotics to treat sleeping sickness and syphilis.

1881-1951 Alexander Fleming discovered penicillin and lysozyme.

1864-1920 Dmitri Ivansvski discovered the first virus which is known as the

tobacco mosaic virus (TMV)

An Overview of Biological Basics



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EXPLOIT THE USEFUL MICROBES. / COMBAT THE HARMFUL ONES.YOU CAN’T BE TOTALLY FREE OF THEM.

Industrial Microbiology

Medicinals, food supplements, alcoholic beverages, enzymes and organic acids _ these are some of the

substances produced on a commercial basis by using microorganisms. The beneficial chemical activities

of microorganisms like bacteria, yeasts, molds and algae are exploited to obtain valuable products from

these organisms after they have been grown in a relatively inexpensive medium.

Industrial Microbiology and Food processing:

Yeast is used make breads, baked goods, alcohol, yogurt and other foods and

drink items.

Today’s yeast are specially engineered to work in large scale industrial

applications.

Specialized bacteria and molds are used to make cheeses of different types.

Biofertilizers include bacteria such as Rhizobia that fix nitrogen.

Food additives increase nutritional value, retard spoilage, change consistency

and enhance flavor. These may be natural compounds such as guar gum and

xanthan gum or flavor enhancers and vitamins.

Industrial Microbiology and Medicine:

Biosensors are monitors used in the detection of specific targets in the

environment, human body or other organisms.

Antibiotic production is a capacity that many microbes have naturally.

Microbes have been developed as a drug delivery system.



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Lactic acid bacteria (LAB) has been exploited to make and deliver vaccines and

other bioactive materials.

Microbes have been developed that degrade oil so that they it may be more

easily extracted.

Industrial Microbiology and Economics:

In the cosmetic industry the botulism toxin derived from Clostridium botulinum is

utilized.

Biopesticides have been developed for the control of insect, nematodes and

other pathogens that effect plants.

Synthetic energy fuels such as ethanol, methane, hydrogen and hydrocarbons

are produced by microbes.

Gasohol which is a 9:1 blend of gasoline and ethanol is a popular fuel alternative.

The ethanol is produced as a by product of yeast fermentation.

Microbes have been used in mining. An example of this is the recovery of metals

is facilitated by bacteria by helping to solubilize it making it more easily extracted.

Microorganisms have been used to clean up the environment in a process called

bioremediation. In bioremediation a microbe is introduced into an environment

where its natural metabolism results in the detoxification or break down of

hazardous chemicals or pollutants.

Specialized Microbes:

Rhizobia are bacteria that fix nitrogen and make it available for plant nutrition and

growth. They form nodules on the roots of legumes. Azolla is a fee floating water plant that fixes nitrogen in association with

cyanobacteria. It acts as a renewable biofertilizer.

Azotobacter are nitrogen fixing bacteria that do not form nodules on plant roots or

associate with legumes. They are free living and in addition to fixing nitrogen they

can produce antibiotics and beneficial growth substances.

Azospirillum fix nitrogen inside plant roots. They produce beneficial compounds

for plant growth and can survive in wetland conditions as well as soils.

Mycorrhiza are fungi that form symbiotic relationships with plant roots. Vesicular

arbuscular mycorrhiza (VAM) is the most important member of this group. VAMcolonies take up nutrients and water which is available for the plant and they act

as root extensions.



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Microbiology: Study of structures and activities of microorganisms.

Form, Structure, Reproduction, Physiology, Metabolism and Identification.

Distribution in Nature

Relationship to each other and to other living things.

Beneficial and detrimental effects on humans, animals, plants.

Physical and chemical changes they make in the environment

Microorganisms are unicellular or consist of same kind of cells held together.

Higher Organisms have a hierarchy of organization: Cells > Tissues > Organs >

Organ systems > Organism.

Cell is the smallest unit of living things that can maintain its structure and reproduceitself in its suitable environment. Cell is the true basic unit of life.

Viruses: Viruses are not cellular organisms. Viruses are obligate intracellular parasites

of living host cells. Viruses are particles that represent the border line of life. They can

reproduce themselves by being parasites on cells of living things, destroying the host

cells. There are viruses which use animal, plant or human cells as their hosts being

specific to one kind of host.

Haeckel’s three kingdom classification of microorganisms:

Plants [Protista] Animals

Haeckel (1866), a German zoologist suggested a third kingdom Protista to include thoseorganisms that are not typically plants and animals. Bacteria, cyanobacteria, algae,fungi and protozoa are cellular organisms placed under protista. Bacteria andcyanobacteria were lower protists while algae, fungi and protozoa were higher protists.

The cells of living organisms are either procaryotic or eucaryotic in nature and there isnot any intermediate condition. The size, shape, morphology and the internal cellular organizations are different in these two groups.

Protista:

Procaryotic: Eubacteria, Archaebacteria, Cyanobacteria

Eucaryotic: Fungi (Molds and Yeasts), Algae and Protozoa



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Procaryotic cells do not have a membrane enclosing a nucleus, and are smaller in size

and have simpler internal constitution in comparison with the eucaryotes. Procaryotes

are organisms with primitive type of nucleus lacking a well-defined membrane, a less

complex nuclear division than mitosis. The nuclear material is a DNA molecule in

prokaryotes compared to chromosomes of higher organisms. Cell wall is made of

peptidoglycan (murein or mucopeptide), a component that is absent in eucaryotic cell

walls.

Eukaryotes are organisms with cells having true nuclei enclosed in a nuclear membrane

and are structurally more complex them prokaryotes. A varying degree of localization of

cellular functions in distinct membrane bound intracellular organelles like nuclei,

mitochondria chloroplasts etc. are occurring in eucaryote cells. Eucaryotes have

membrane bound organelles. Their DNA is complex and typically associated with

structural and regulatory proteins and it is contained within a membrane bound nucleus.

The cells are about ten times larger than those of prokaryotes. Some eucaryotes (e.g.

plants) have cell walls but are not made up of peptidoglycan molecules.

Replication in eucaryotes involves mitosis and meiosis. Meiosis occurs in sex cells like

sperm and egg. The eucaryote cell member is a fluid phospholipid bilayer containing

sterols and carbohydrates. The membranes can endocytose, phagocytose, pinocytose

and exocytose.

In Meiosis a diploid parent cell creates four haploid daughter cells. The DNA has usually

undergone some crossing over so the chromosomes are not only halved but are also

changed through rearrangement.

Mitosis: Cells have two main stages in the life cycle. Interphase: the cells grow and

duplicate their DNA, in the second stage the cell’s nucleus divides. In mitosis nuclear

division starts after the cell has duplicated its DNA. The result is two exact copies of the

DNA.

Whittaker (1969) proposed five kingdoms based on three levels of cellular organization

and three principal modes of nutrition, photosynthesis, absorption and ingestion. The

prokaryotes lacking ingestive mode of nutrition are included in the kingdom. Monera.

In the kingdom Protista unicellular eukaryotic microorganisms representing all the three

modes of nutrition are included.The multicellular green plants and higher algae were placed in the kingdom Plantae

while multinucleate higher fungi in the kingdom Fungi and the multicellular animals in

the kingdom Animalea.



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Introduction to Bacteria:

Coccus

Chain = Streptoccus

Cluster = Staphylococcus

Bacillus

Chain = Streptobacillus

Coccobacillus

Vibrio = curved

Spirillum

Spirochete

Square

Star

Morphological

Traits

Shape

Flagella,

Fimbriae,

pili

Capsule and slime

layers

Colonial

Morphology

Gram

staining



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The characteristic compound found in all true bacterial cell walls is peptidoglycan.

The Gram staining process includes the use of:

a primary stain (crystal violet)

a mordant (helper) iodine solution,

a decolorizer (95% ethanol),

a counterstain (safranin).

Gram-positive cell walls Gram-negative cell walls Thick peptidoglycan

90% peptidoglycan

Teichoic acids

1 layer

Not many polysaccharides

In acid-fast cells,

contains mycolic acid

Thin peptidoglycan

5-10% peptidoglycan

No teichoic acids

3 layers

Outer membrane has lipids,polysaccharides

No acid- fast cells (mycolic

acid)



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Classification on the bases of source of carbon, electron and energy

Carbon Sources

Autotrophs CO2 sole or principal

biosynthetic carbon source.Heterotrophs Reduced, preformed, organic

molecules from other

organisms

Energy Sources

Phototrophs Light

Chemotrophs Oxidation of organic or

Inorganic compounds

Electron Sources

Lithotrophs Reduced inorganic molecules Organotrophs Organic molecules



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Archaebacteria have distnictive chemistry. Originally thought to exist only in extreme

environments, archaea are now found to be ubiquitous in soil and water, and even in

the human digestive tract. Included are the thermophilic Crenarchaeota, such as

Sulfolobus and Pyrodictium, as well as mesophilic crenarchaeotes and even sponge

endosymbionts. They cover the salt-loving Haloarchaea, the methanogens, and the

elusive Nanoarchaea, whose tiny size pushes the limits of viability.



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Notes for Microbiology