Microbiology Unit 2-3: Bacteria

Microbiology and Parasitology

UNIT 2/3: BACTERIA

Microbiology

Virus: Ebola

Algae: Algal bloom

Fungi: MushroomBacteria: Salmonella

?ENEMY OR… …FRIEND

Test your memory

A. True or False1. Microbiology is the study of disease-causing microorganisms2. Microbes are involved in the production of food and drinks3. Fungi are a type of acellular microorganisms4. The majority of our microflora are “microbial allies”5. Microbial intoxication is a type of infectious disease

B. Multiple choice1. Who invented the microscope

a) Pasteur; b) van Leeuwenhoek; c) Fleming

2. Koch’s Postulates proves thata) Microbes can be isolated from an infected animal; b) Microbes are always found in the same animal species; c) Specific microbes cause particular diseases

3. Ignaz Semmelweis is reffered to asa) Father of Microbiology; b) Father of Handwashing; c) Father of Hygiene

Variety of Microbes

• Categories– Acellar: Viroids, Virus, Prion– Prokaryotes (cellular without nucleus): Bacteria, Archaea, Cyanobacteria– Eukaryotes (cellular with nucleus): Algae, Fungi, Protozoa

Microbes

Acellular ViroidsPrions

Virusus

Cellular

ProkaryotesArchaeaBacteria

Cyanobacteria

EukaryotesAlgaeFungi

Protozoa

Today

• Classification– Taxonomy– Morphology

• Structure of cells• (Endo)spores• Cell reproduction

– Binary fission– Generation time

• Bacterial growth– Encouraging growth– Inhibiting growth

• Staining• Other characteristics• Unique bacteria

– Rickettsia

Microbial classification

• Millions of species on Earth– Bring order in the chaos: system to classify organisms– Taxonomy = science of classification of species– Classification, nomenclature and identification (complicated system)– Scientist still debate about the system

Burton’s Microbiology: Chapter 3,4

233277

182871

5007

Only 1% known?

3 or 5?

Classification by shape

• Categories based on shape of their cells (simpler system)– Spherical: cocci– Rod-shaped: bacilli– Short rods/elongated spheres: coccobacilli– Curved/Spiral-shaped: spiralla (spirochetes)– Various shapes: Pleomorphic (cell wall-deficient bacteria)

BacilliCocci Curved/spiral

Burton’s Microbiology: Chapter 4

Morphology of cocci


Chains

Clusters

• Bacteria aggregate: morphological arrangement

Morphology of bacilli

Chains: streptobacilli

Side-by-side: DiphtheroidsPairs: Diplobacilli

Short rods: Coccobacilli


Morphology of spirochetes

Less tightly coiledTightly coiledhighly flexible cell wall

able to move through tissue

Treponema pallidum: Syphilis

Borrelia:Lyme disease


Size of bacteria

• Spherical bacteria: Coccus– Typical diameter: 1 μm (1 million micrometers = 1 meter)– Seven cocci fit the diameter of human red blood cell

• Rod-shaped bacteria: Bacillus– Typical length: 3 μm– Typical width: 1 μm


?

Structure: Advanced microscopes

(Optical) Light Microscopex1000

Scanning Electron Microscope (SEM)

x10.000

Transmission Electron Microscope (TEM)

x100.000

1 μm

“STAPHYLOCOCCCUS AUREUS”

Burton’s Microbiology: Chapter 2,3“Study the structure of cells in detail”

Cell structure


• Cell– Fundamental unit of a living organism– Basic characteristics of life

• Cell = tiny functional factory– Metabolism: all chemical reactions in a

cell– Use food (nutrients) to produce energy– Grow and reproduce– Responds to environment– Can mutate (change genetically)

• Study of cell structure– Cytology

Procaryotic cell

• Bacteria: Procaryotic cell– Cell envelope

• Cell membrane• Cell wall • Slime layers and Capsules

– Chromosome– Cytoplasm

• Cytoplasmic Particles– Flagella and Pili– (Endo)spores


Difference with eucaryotes:10x smaller than eucaryotic cellLess complex cell structure: no nucleus

Cell envelope

• Cell membrane– Flexible thin skin that encloses the cells

interior– Controls in/out transport of substances

(via proteins in membrane)

• Cell wall– Provide rigidity, strength and protection– Different structure for Gram+ and Gram-

bacteria– Cell wall-deficient (CWD) bacteria: cause

chronic diseases, e.g. Lyme

• Glycocalyx (external layer) – Slime layer: slide along solid surfaces– Capsule: protection (white blood cells)


Bacterial genome


• Genome carries genetic information (3000 genes)

– Chromosome• Duplicating itself• Guiding cell division• Directing cellular activity• Embedded in cytoplasm

– Plasmid

Nutrient matrix

• Cytoplasm– Semifluid nutrient matrix of cell

• Cytoplasmic particles– Complex mixture of all materials required for metabolic functions of cell– Mostly ribosomes, sites for protein synthesis


Flagella and Pili

• Flagella– Threads of protein– Movement: flagellated bacteria

are motile– Number and arrangment vary


• Pili (fimbriae)– Hair-like structures (gram-)– Rigid, not associated with

movement– Adhere/attach to surfaces

(e.g. human body tissues)– Sex pilus: transfer of genetic

material (plasmid) from one bacteria to another

Salmonella cell

Spores


• Endospores (some bacteria)– Thick protein coat– In order to survive when moisture

or nutrient supply is low– Resistant to

heat/cold/drying/chemicals

• Sporulation– Process to form endospores– Copy of chromosome (most

valuable) and cytoplasm enclosed

• Germination– Dried spore lands on moist

nutrient-rich surface– New bacterial cell emerges (a seed)

Terminal spores

Subterminal spores

Cell reproduction

• Binary fission (reproduction)– Chromosome is duplicated

(DNA replication)– Parent cell splits in half to

become two daughter cells– Daughter cells contain same

genetic info as parent cell

Burton’s Microbiology: Chapter 3Binary fission

Generation

• Generation time – Time it takes to splitt cells– Depends on species and conditions (pH, T, nutrients)

• Slow and rapid growers– E. coli: 20 minutes (ideal conditions)

• Mathematics– What time does E. coli need to reach a population of 1.000.000, starting

from just two bacterial cells?


Bacterial growth


Encouraging/Inhibting growth

MICROBIOLOGY LABORATORY

In vitro: outside the body

Artificial culture media

Growth requirements

Inoculate & Incubate

Population growth curve

Factors affecting growth

• Fundamental needs of microbes– Nutrients: energy sources (C, H, O, S, P, N)– Moisture: Water– Temperature: thermophiles or pshychrophiles– pH: acidity or alkalinity– Pressure: Osmotic (cell membrane) and barometric pressure (atmosphere)– Atmosphere: O2 and CO2


Encouraging growth

• Bacterial growth– No increase in size, but increase in number (multiplication)– Binary fission results in bacterial colony– Control the (ideal) conditions for optimum growth

• Culture media in the lab, artificial– Content: chemically defined / complex– State: solid / liquid– Growth: selective / differential

• Culturing bacteria in the lab, in vitro– Clinical lab: Enable identification of pathogens– Research lab: Study, harvest antibiotics, produce vaccines– Industry lab: Produce microbes for food/beverage companies


Selective: only Gram-

Differential: lactose-fermenters turn pink

Culture bacteria

1. Inoculate– Add bacteria (specimen) to medium– Sterile: prevent contamination

2. Incubate– Chamber with appropriate conditions– Monitor temperature and atmosphere


3. Count population– Determine bacterial growth– Bacterial population growth curve

• Lag: absorb nutrients • Log: binary fission (growth)• Stationary: lack of nutrients• Death: toxic waste

Innoculation of solid agar

Growth

EXPERIMENT 001Title: Potato germsTopic: Growth of bacteria

1. Peel and slice potato (with gloves) in 4 pieces of equal size

2. Put one slice (with gloves) in box labeled “control”

3. Put second slice (with gloves) in box labeled “oral” and cough/blow on it

4. Take third slice and rub it on the table before putting it in box labeled “table”

5. Take out your gloves and rub fourth slice with your hands before putting it in box labeled “hands”

Inhibiting growth

• Physical methods– Heat / Cold– Heat + pressure– Desiccation (freeze-drying)– Radiation / Ultrasonic waves– Filtration– Gaseous atmosphere

• Chemical methods– Disinfection (soap/alcohol)

• Chemical agents on materials (nonliving)

– Antisepsis (prevent infection)• Chemical agents on body

(living)

“Inhibiting: from reducing microbial growth to killing pathogens”


Classification by staining

• Observing microbes– Bacteria are colorless, transparent: difficult to see

• Examine bacteria via staining– Smear– Dry– Fix

• Kills organisms• Preserves morphology• Anchors to slide

– Observe cell morphology• Size• Shape• Arrangement• Cell walls, capsules, flagella, endospores


Simple stain

Dye: methylene blue


• Determine shape and morphological arrangement

Gram staining (1)

• Gram staining procedure– By Dr. H.C. Gram (1883)– Most important staining method

• Differentiates Gram- / Gram+

• Color depends on cell wall structure– Gram+ = blue-to-purple– Gram- = pink-to-red


Gram staining (2)

Gram negative

Gram positive


Result of Gram staining

Overview of staining

• Acid-fast staining– To stain gram-variable bacteria (Mycobacterium)

• M. tuberculosis in sputum of TB patient• M. leprae


Acid-fast TB bacilli

Characteristics of bacteria

• Characteristics used to identify bacteria

• Already discussed…– Cell shape (cocci, bacilli, spiral-shaped, etc.)– Morphological arrangement (chains, clusters, pairs, coiled, etc.)– Staining reactions (gram+, gram-, no cell wall)

• But there is more…– Motility– Colony morphology– Atmospheric requirements– Nutrional requirements– Biochemical and metabolic activities– Pathogenicity– Genetic composition


Motility

• Motility of bacteria– Bacterium is able to “swim”– Associated with presence of flagella– Determined with semisolid agar method

• Pattern of growth of nonmotile organism– Turbidity only seen along stab line– Most cocci are unmotile

• Pattern of growth of motile organism– Turbidity throughout the medium– Most spiral-shaped and half of bacilli


Semisolid agar method

Colony morphology

• When bacteria divides over and over…– … the result is a colony– Colony contains millions of microbes– Morphology varies in:

• Size (indication for growth rate)• Color• Shape• Elevation• Appearance at edge


Atmosphere

• Classify bacteria on relationship to O2 or CO2


Require ~20% O2

Prefer ~5% O2

Require 0% O2

Prefer 0% O2

No preference

Majority of clinical specimens

Nutrition and Activities

• Biochemical and metabolic activities – Characterize by waste products

• Secretion of enzymes or gases

• Nutritional requirements– All: C, H, O, S, P, N– Some: K, Ca, Fe, Mn, Mg, Co, Cu,

Zn, U, vitamins– Demanding: Fastidious (fussy)


Pathogenicity


• Ability to cause disease– Many pathogens are

able to cause disease due to…

• Capsules• Pili• Endotoxins• Exotoxins• Enzymes

– …which damage cells and tissues

Genetic composition

• Molecular diagnostic procedures– Modern labs: analyze DNA or RNA of bacteria– Identify organism by composition of genetic material– Determine relatedness between two species


Unique bacteria

• Rudimentary (unique) bacteria: different from the others…– Rickettsias & Chlamydias

• Pathogen must live within host cell (like a virus)– Mycoplasmas: lack cell walls

• Occur in many shapes: pleomorphic• No Gram staining possible• Resistant to treatment with penicillin• Can be free-living or parasitic pathogens

– Megabacteria (750 μm) & Nanobacteria (20 nm)

• Photosynthetic bacteria– Use light as energy source– e.g. Cyanobacteria

• Produce oxygen, oxygenation of the atmosphere• Like blue green algae that overgrow lakes (toxic)


Rickettsias (1)

• Unique bacteria: Rickettsias– Named after Howard T. Ricketts– Gram- cell wall– Obligate intracellular pathogen

• Must live within host cell • Cannot grow on artificial (synthetic)

culture media• Grow inside eggs/animals/cell cultures

– Disease (transmitted by lice, fleas, ticks)• Rickettsialpox• Epidemic and Endemic typhus• Rocky Mountain spotted fever

– Medicine: Tetracyclines• Attack bacterial ribosomes

(site for protein synthesis)

Burton’s Microbiology: Chapter 4,8,9

Rickettsias (2)

• Obligate intracellular pathogen– Invade and live in host cells– Produce their own proteins and RNA/DNA– Still require intracellular environment:

“leaky membranes”

• Intracellular survival mechanisms– Attack: Phagocytes (like white blood cells)

protect body, destroy pathogens– Protection: Rickettsias produces enzymes that

destroy the interior of the phagocytes


The End

Date post:	17-Aug-2015
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Microbiology Unit 2-3: Bacteria

Education