Microbiology CSCC Exam 1

Microbiology

A branch of biology, that deals with all members of the microbial world

Classes of Microbiology

Bacteria, Fungi, Protozoa, Algae and "viruses."

Beneficial Bacteria

The majority of the bacteria are beneficial. Only about 3% are harmful.

Examples of benefits we get from bacteria and fungi include

Bacteria and fungi decay organic matter.

Most antibiotics are made by bacteria and fungi.

Normal flora contribute to health.

Intestinal bacteria are involved in production of vitamins K & vitamin B.

Bacteria are used to make ethanol, pesticides and dietary amino acids.

Bacteria degrade oils, clean natural and artificial oil spills.

More than 50% of photosynthesis is performed by microorganisms.

Girolamo Fracastoro

Frst to realize that microorganisms are involved in causing diseases

Robert Hook

Frst to observe cell and coin the word cell "Cella". He also introduced cell theory..

Anton Van Leeuwenhoek

was the first to observe bacteria and classify bacteria into:

Cocci (round).

Bacilli (rods).

Spirilla (spiral).

Cocci

Round

Bacilli

Rods

Spirilla

Spiral

Spontaneous generation

a belief that stated, organisms such as mice, toads, flies and maggots could be generated from manure or hay.

Lazzaro Spalanzani

boiled broth in glass with sealed necks and demonstrated microbes are killed by heat and spontaneous generation does not exist.

Francesco Redi

placed meat in wax sealed or gauze-covered jars and demonstrated maggots were not generated spontaneously.

John Tyndall

showed some life forms require 5 minutes of boiling to die and others 5 hours.

Ferdinand Cohn

discovery of endospores

Robert Koch

was able to establish the role endospores play in disease transmission.

discovered Mycobacterium tuberculosis, Vibrio cholerae, isolated Bacillus anthracis, and developed the idea of pure cultures.

Louis Pasteur

disproved spontaneous generation by boiling nutrient broth in swan-necked flasks. Pasteur also introduced, pasteurization, immunization procedures, produced vaccines for anthrax and rabies and discovered role of yeast in fermentation.

Joseph Lister

introduced aseptic techniques used in surgery using disinfectants in operating rooms, hands, dressings, instruments and air.

Alexander Fleming

discovered penicillin (the first antibiotic discovered!)

Chain and Florey

purified, tested and made production of penicillin in large amounts

Ross & Grassi

discovered the vector for malaria is the female Anopheles mosquito (causative agent for malaria).

GOLDEN AGE OF MICROBIOLOGY

1854 -1918

Vaccines can be prepared using...

1.Live organisms.

2.Attenuated(live weakened organisms).

3.Killed organisms.

4.Recombinant or engineered products.

Edward Jenner

inoculated an 8 year old boy with cowpox and proved vaccine against small pox was effective.

influenza in the 1918

More people died worldwide by influenza in the 1918 epidemic ALONE than those who died in,

1.World war I

2.World war II,

3.Korean War and

4.Vietnam war, all combined!

TB

Tuberculosis (TB) is caused by an acid fast organism called M. tuberculosis.

TB is transmitted by close contact and inhalation.

Its cell wall contains wax-like material therefore, it resists drying.

TB is very difficult to treat and multidrug resistant M. tuberculosis is now common.

There is a vaccine for TB which is called BCG.

Leprosy

M. leprae is an obligate intracellular parasite.

Three Domains

Bacteria, Archaea, Eukarya

Domain Bacteria

Are prokaryotes and have rigid cell walls.

Have no membrane bound nucleus or organelles.

The three most common bacterial shapes are; Cocci, Bacilli, Spiralla.

Domain Archaea

They have similar shapes like bacteria.

Cell walls of Archaea do not have peptidoglycan.

Some Archaea can grow at 1210C.

Archaea can grow in high salt concentration.

Domain Eukarya

Domain eukarya includes; Algae, Fungi, Protozoa, Animals and Plants.

•All Eukaryotes have true cells, i.e. have membrane bound nucleus and organelles.

•Eukaryotic cells DO NOT have peptidoglycan.

•Algae and fungi have rigid cells.

•Algae perform 90% of all photosynthesis

•Algae are aquatic, photosynthetic and free living.

•Fungi and protozoa depend on other organisms for their energy source.

•Protozoan cells do not have rigid cell walls.

Bright-field Microscope

Uses visible light to observe objects, and produces a maximum magnification of a 1000x.

Magnification

The total magnification obtained by a microscope depends on the lenses used to magnify objects. Total magnification is obtained by multiplying the magnification of the ocular lens by magnification of objective lens used (e.g. 10x X 100x = 1,000x).

Resolution

Resolving power of a microscope is its ability to distinctly show two closely positioned points as two distinct and separate points. Resolution depends on the quality of lenses and wavelength of the illuminating light.

Immersion lens

Use of a drop of oil increases light that passes through the objective lens and helps with getting a clear image of the organisms or object being observed.

Phase-Contrast microscope

amplifies differences between refractive index of cells and surrounding medium, by a set of a set of rings and diaphragms to achieve resolution. Higher contrast can be achieved by staining the specimen.

Dark-field Microscope

In a dark-field microscope, the object will appear bright on a dark background.

Fluorescence Microscope

In a fluorescent microscope, fluorescent molecules absorb ultraviolet light and emit visible light. The image fluoresces on dark background.

Transmission Electron Microscope

is used to observe fine details. This microscope directs a beam of electrons at specimen.

Scanning Electron Microscope

is used to observe surface details. In this microscope, a beam of electrons scan surface of specimen.

Bacterial Cell Membrane

Bacterial cell membranes are made of phospholipids, proteins and carbohydrates.

Teichoic acid component of peptidoglycan gives the cell negative charge.

Diffusion

the process by which molecules move in and out freely across the cytoplasmic membrane (no energy required).

Osmosis

Is diffusion of water across a membrane.

Bacterial Cell Wall

Rigidity of cell wall is due to peptidoglycan (PTG), which is found ONLY in bacteria.

Penicillin acts on the peptidoglycan layer, therefore, it is more effective on Gram positive bacteria.

Gram positive bacteria

Have a thick peptidoglycan layer, constituting 60-90% of cell wall with up to 30 layers of peptidoglycan. But don't have an outer phospholipid membrane.

Have teichoic acids which regulate ionic movement, prevent autolysis and are involved in growth of lipoteichoic acids. The cell wall gets its acidic charges from these molecules.

Gram negative bacteria

Is more complex than G+ cell wall.

It contains a single thin layer of peptidoglycan sandwiched between outer membrane and cytoplasmic membrane.

Have lipopolysaccharides (LPS).

lipopolysaccharides (LPS)

consists of three parts: Lipid A, Core and CHO side chains.

Capsules

external viscous structures on surface of some made of sticky glycocalyx (polysaccharide) coating.

Capsules contribute to virulence

Capsules enhance bacterial adherence to surfaces.

Bacteria that form endospores

Clostridia and Bacillus

Endospores

Only 1 endospore per cell is produced.

Bacterial endospores are the most resistant life forms.

Endospores withstand extreme heat, drying, freezing, radiation, and chemicals.

Bacterial movement

Active bacterial motion is regulated by flagella

types of bacterial flagella are:

A.Monotrichous A single flagellum at one end.

B. Lophotrichous Several flagella on one end.

C. Amphitrichous Single flagellum on each side.

D. Peritrichous Flagella all over bacterial cell.

fimbriae

used for attachment rather than for movement.

Pili

Conjugation pili (sex pili) are used as DNA transfer tubes from one bacterium to another .

Attachment pili are used by bacteria to adhere to surfaces. These contribute to pathogenicity.

two types of staining procedures

1.Simple staining; only One dye is used.

2.Differential staining; Two or more dyes are used.

Acid-fast staining

(differential staining)

Add carbol fuchsin (primary stain) then heat over flame for few minutes.

2.Wash and then add a decolorizer (5% HCl and 95% ethyl alcohol) to remove primary color from non-acid-fast organisms. Acid-fast bacteria will retain the primary color.

Bacterial Growth

All bacteria are prokaryotic and divide by binary fission

Generation time

The time it takes for one cell to divide to two cells

Biofilms

important because pathogenic bacteria in a biofilm resist immune responses and antimicrobials.

increase survival and attaching to surfaces.

Pure cultures

can be obtained by:

•Streak plate or

•Pour plate method.

Essential elements and Trace elements required for bacterial growth:

•Essential elements required for growth are Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium and iron.

•Trace elements are required for growth but are needed in small amounts e.g. Cobalt,

Complex media

have no exact chemical formula of the ingredients in them. Examples include; Nutrient broth, Blood agar, Chocolate agar.

Chemically defined media

are composed of precise amounts of pure chemicals.

Selective media

inhibit growth of unwanted organisms and allow only sought after organisms to grow.

Thayer-Martin agar used for isolation of Neisseria gonorrhoeae and MacConkey agar used for isolation of Gram-negative bacteria.

Differential media

contain substance that bacteria change in recognizable way

e.g. Blood agar is sued to see hemolysis; MacConkey agar, is used to differentiate lactose fermenters and non fermenters.

Photoautotrophs

use sunlight and CO2 to manufacture their own food.

Chemolithoautotrophs

use inorganic carbon for energy and CO2 as carbon source

Photoheterotrophs

derive their energy from sunlight and carbon.

Chemoorganoheterotrophs

use organic compounds for energy and carbon source. This is the method used in humans and all other animals.

ubiquitous Microorganisms

can be found in hot, cold, saline, alkaline, acidic, neutral, oxygen free, air and toxic environments.

Macronutrients

nutrients needed in large amounts like, lipids carbohydrates, and proteins (organic nutrients).

Micronutrients

are essential nutrients, required in trace amounts like manganese, zinc, and nickel (inorganic nutrients).

4 stages in a bacterial growth are:

Lag phase, Exponential (Log), Stationary, Death

Lag phase

stage where bacteria adapt to the growth environment, increase in size, and repair cell components.

Log phase

stage where bacteria grow exponentially. At this stage bacteria are MOST sensitive to antibiotics.

Stationary phase

stage where bacterial population remains constant, nutrients are depleted and toxic materials increase.

Death phase

stage where nutrients are depleted and more bacteria die than are generated.

Psychrophiles

bacteria such as Staphylococci and Listeria monocytogenes can grow or survive between temperatures of -20o20o C.

Mesophiles

are bacteria that grow between the temperatures of 20 50oC.

Thermophiles

are bacteria can grow between 50110o C.

optimum pH for bacteria

6.5 to 7.5.

Obligate aerobes

require oxygen and can detoxify toxic oxygen byproducts like O2-, H2O2, OH- and OCl-.

Facultative anaerobes

can live in the presence or absence of oxygen. They catalase and superoxide desmutase. Their metabolism can occur by aerobic respiration or anaerobically by fermentation.

Obligate anaerobes

die if exposed to oxygen.

Hypertonic

The solute concentration is greater outside the cell, thus water leaves the cell and the cell shrivels.

Hypotonic

The solute concentration is less outside the cell. Therefore, water enters the cell and may burst it

Isotonic

The solute concentration is equal inside & outside cell. Hence, the net movement of water molecules in and out of the cell is the same.

Viruses

non-living infectious agents and have different sizes, shapes and nucleic acids.

may be bacteriophages, plant viruses or animal viruses.

may be enveloped or naked , and have either DNA or RNA not both.

Are obligate intracellular, are metabolically inert when they are outside the cell they can infect.

Each virus type infects only a specific organism(s) or cell type.

Viral structures

A viruses consists of a nucleic acid surrounded by a protein coat.

•The protein coat is knows as a capsid.

•Subunits of a capsid are called capsomeres.

Viral envelopes

are modified pieces of host's cell membrane. Most cell membrane proteins are replaced by viral proteins, such as the spikes.

Capsids

found on all viruses, are proteins that surround the nucleic acids.

Capsids are made of identical unit proteins called capsomeres.

Each virus has a specific number of capsids.

Viral life cycle

Adsorption

Penetration

Biosynthesis

Assembly

Release

Release of viruses

by budding or lysis.

DNA viruses

replicate and assemble in the nucleus of the host cell.

RNA viruses

replicate and assemble in the cytoplasm.

lytic pathway

burst from the host cell and the cell dies.

lysogenic pathway

viral DNA integrates to the host cell DNA, becomes a provirus and continues to make copies

HIV

often remains latent

•HIV has an RNA genome, therefore, it must produce a DNA copy before incorporating genes into the host's DNA

Latent infections

after primary infection subsides, some viruses may stay dormant in some parts of the body for years and reactivate in the future. An example of this is chickenpox → Shingles

Chronic infections

the virus is present at all times during the infection. Examples of chronic infections are; Hepatitis B and Hepatitis C.