Transcript Bacteriology - Dr. Roberta Dev Anand

EDUCATION
“The purpose of education is to
replace an empty mind with an open
one.”
Bacteriology

1st observed by Leeuwenhoek – 1676 with single
lens microscope
Definition - Bacteria
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
Single-celled microorganisms with a variety of shapes (spheres,
rods, spirals)
Bacteria are prokaryotes
 Genetic material contained in a single circular chromosome
in the cytoplasm of the cell (nucleoid)
Prokaryotic

Prokaryotic
 Fewer organelles & smaller
than eukaryotes
 Cell wall
 +/





capsule
Cell/ plasma membrane
Nucleoid
Cytoplasm
Ribosomes
+/-: pili, plasmids, flagellum
Few have endospore

Eukaryotic
 Cell / plasma membrane
 Nucleus
 Nucleolus
 Cytoplasm
 Mitochondria
 Golgi apparatus
 Endoplasmic reticulum
 Ribosomes
 Vacuoles
 Lysosomes
Bacteriology


Grow in various kinds of environments; extreme
Without bacteria life as we know it would cease to
exist!
Bacteriology


Bacterial cells outnumber the other cells in our
bodies by 10:1!
Majority are harmless or beneficial
 Ex:

Digestive tracts of people and animals
Few cause infectious disease
 Most
common – respiratory diseases
Bacteriology – Morphology

Wide variety
 Spherical
–
cocci/coccus
 Rod – bacilli/bacillus
 Single cells, pairs,
chains, clusters
 Elongated to form
filaments
Bacteria
Gram positive cocci: Staphylococci
Bacteriology – Cellular Structure

Cell membrane
 Barrier
to hold nutrients, proteins and other components
of cytoplasm within cell
 No membrane-bound organelles – few intracellular
structures
 No
nucleus, mitochondria, chloroplasts, golgi apparatus and
endoplasmic reticulum

Genetic material – single circular chromosome
 In
nucleoid in cytoplasm
FEW BACTERIA HAVE ABILITY TO PRODUCE ENDOSPORES
Persists in variable environment
Not membrane bound
Hairlike protein extensions
Attach/communicate with
Other cells
Smaller than Eukaryotic
Mobility
Barrier against
phagocytosis
DNA outside chromosome
Replicate independently
Pass info via pilus
Bacteriology



Treat infections with antibiotics
Also used for agricultural processes
Industrial processes
 Waste
treatment
 Cheese and yogurt production
 Manufacture of antibiotics and other chemicals
Bacteriology – Extracellular Structures

Cell wall – around cell membrane
 Essential
to survival of many bacteria
 Penicillin
2
kills by inhibiting a step in synthesis of cell wall
types
 Gram
positive – thick cell wall with many layers
 Gram negative – thin cell wall
 Based on reaction to Gram stain
 Differences in antibiotic susceptibility
Gram Staining

The bacterial kingdom is subdivided into main
categories by a process called Gram Staining (named
after Hans Christian Gram, a Danish bacteriologist).
The process is a stain that illustrates the composition
of the cell wall.
The gram stain consists of these steps:
•
Crystal violet - stains both
gram negative and positive
bacteria
Gram's iodine - fixes the stain
in gram positive bacteria
Ethanol or acetone - washes
the stain from gram negative
bacteria
Safranin - counterstain, will restain gram negative bacteria
while not interfering with the
previous stain in gram positive
bacteria
Gram stain Procedure
Staphlylococcus sp.
Streptococcus sp.
Salmonella sp.
Proteus sp.
Bacteria - veterinary medicine
GRAM NEGATIVE
GRAM POSITIVE
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
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Cocci
 Staphylococcus species
 Streptococci
Rods
C: Coyrnbacterium pseudotuberculosis
L: Listeria monocytogenes
E: Erysipelothrix rhusiopathiae
A: Arcanobacterium pyogenes
R: Rhodococcus equi.
Endospores: Clostridium (anaerobes) and
Botulinum
Anaerobes: Actinomyces bovis
Acid fast: Tuberculosis

Gram negative enteric rods
 Klebsiella
 Proteus: UTI
 E. coli: UTI
 Salmonella
 Shigella
Gram negative non enteric rods
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Pseudomonas aeruginosa
Pasteurella multocida
Moraxella bovis
Anaerobes: Bacteroides, fusobacterium
Campylobacter: spiral twisted
Rickettsia and Chlamydia
Bacteriology – Extracellular Structures
•
Glycocalyx (a network of polysaccharides)
–
Surrounds the cell wall
•
Varies in structural complexity
–
–
–
–
–
–
Disorganized extra-cellular polymer = slime layer
Highly structured = capsule
Protect from engulfment by macrophages
Act as antigens
Cell recognition
Allows attachment to inert surfaces (teeth, rocks, etc)
Bacteriology – Endospores
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

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Highly resistant, dormant structures
Consist of central core of cytoplasm containing DNA and
ribosomes surrounded by cortex layer
Protected by impermeable and rigid coat
Made by certain genera of Gram-positive rods


Bacillus
Clostridium
Bacillus vs. Clostridium
Slides can then be transported to a laboratory or stained in the field with
New Methylene Blue or a Wright’s stain kit.
Bacillus vs. Clostridium
Bacillus anthracis, X2000.
Note 2 main characteristics:
1. sharp, squared ends
2. pale capsule around bacteria
Clostridium septicum, X2250.
Note 3 characteristics:
1. smaller size
2. no capsule
3. rounded ends
Bacteriology – Endospores
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
No detectable metabolism
Survive extreme physical and chemical stresses
 UV
light
 Gamma radiation
 Detergents/disinfectants
 Heat
 Pressure
 Drying
Bacteriology – Endospores
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

Survive millions of years
Survive exposures to vacuum/radiation in space
Can cause disease
 Inhalation
of Bacillus anthracis endospores
 Contamination of deep puncture wounds with
Clostridium tetani endospores => tetanus
Anthrax
Tetanus
Bacteriology – Pathogens
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
Definition – bacteria or other agent that forms a
parasitic association with other organisms
Major cause of human and animal death and
disease
 Examples:
tetanus, food-borne illness (Salmonella,
Campylobacter, leprosy, Tuberculosis (TB)

Important in agriculture
 Johne’s
disease, mastitis, salmonella, anthrax
Bacteriology – Pathogens

Each species has characteristic spectrum of
interactions with hosts
 Ex:
Staph/Strep => skin infections, pneumonia,
meningitis, sepsis

Can also be part of normal flora w/o causing any
disease
Bacteriology – Pathogens

Some organisms always cause disease
 Rickettsia


– gram (-) obligate intracellular parasites
Ehrlichia
Rickettsia rickettsii (RMSF)
 Chlamydia
– gram (-) obligate intracellular parasite
 Pneumonia
 Urinary

tract infections
Opportunistic
 Primarily
in immune suppressed hosts
Bacteriology – Pathogens

Treatment
 Antibiotics
 Bacteriocidal
 Bacteriostatic
 Many
types – each class inhibits a process in pathogen that
is different from host
Bacteriology – Pathogens

Prevention by using antiseptic measures
 Cleanse
skin with antiseptic prior to needle puncture
 Proper care of indwelling catheters
 Sterilization of surgical and dental instruments

Disinfectants
 Kill
bacteria/other pathogens on surfaces
 Ex: bleach, Roccal, chlorhexidine
Bacteriology – Growth and Reproduction
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Grow to fixed size
Asexual reproduction – binary fission
Can be rapid under optimal conditions
 Double


every 9.8 minutes
2 identical clone daughter cells formed
Can also form more complex reproductive structures
that facilitate dispersal
Bacteriology – Growth and Reproduction

Cultured with solid or liquid media
 Solid
– agar plates – used to isolate pure cultures of a
bacterial strain
 Liquid
 Measurement
of growth
 Large volumes needed
 Selective
 Specific
media
nutrients added or deficient or antibiotics added
 Used to ID specific organisms
Bacterial Reproduction
References
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http://www.sciencebuddies.org/science-fairprojects/project_ideas/MicroBio_Interpreting_Plates.s
html
http://www.vetmed.ucdavis.edu/whc/pdfs/necropsy.
pdf
http://www.vetmed.wisc.edu/pbs/courses/bact/labm
anual/labmanual.html
http://pathmicro.med.sc.edu/fox/enterobact.htm