Transcript Bacteriology - Dr. Roberta Dev Anand

EDUCATION
“The purpose of education is to
replace an empty mind with an
open one.”
Definition - Bacteria


Single-celled microorganisms with a variety of shapes
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 – Growth and Reproduction


Asexual reproduction – binary fission
Can be rapid under optimal conditions
 Double

every 9.8 minutes
2 identical clone daughter cells formed
Bacterial Reproduction
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
Bacteriology – Morphology

Wide variety
 Spherical
–
cocci/coccus
 Rod – bacilli/bacillus
 Single cells, pairs,
chains, clusters
 Elongated to form
filaments
Bacteria
Staphylococci
Bacteria – 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
Bacteriology – Extracellular Structures

Cell wall – around cell membrane
 Essential
 Some
to survival of many bacteria
antibiotics kill by inhibiting a step in synthesis of cell
wall
 Gram
Positive Cell Wall vs. Gram Negative Cell Wall
 Gram
positive – thick cell wall with many layers
 Gram negative – thin cell wall
 Based on reaction to Gram stain
 Differences in antibiotic susceptibility
Bacteria – 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)
Not membrane bound
Hairlike protein extensions
Attach/communicate with
Other cells
Smaller than Eukaryotic
Mobility
Barrier against
phagocytosis
DNA outside chromosome
Replicates independently
Pass info via pilus
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.
Gram Positive Cell Wall vs. Gram Negative Cell Wall





Gram positive – thick cell wall with many layers
Gram negative – thin cell wall
Based on reaction to Gram stain
Differences in antibiotic susceptibility
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
Bacteria – Pathogens


Definition – bacteria or other agent that forms a
parasitic association with other organisms
Major cause of human and animal death and
disease
 Examples:
tetanus, 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
Bacteria – Pathogens

Some organisms always cause disease

Rickettsia – gram (-) obligate intracellular parasites


Chlamydia – gram (-) obligate intracellular parasite



Pneumonia
Urinary tract infections
Opportunistic


Causing tick-borne diseases such as Ehrlichiosis & Rocky Mountain
Spotted Fever
Primarily in immune suppressed hosts
Can also be part of normal flora w/o causing any
disease
Bacteriology – Endospores




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
Bacteriology – Endospores



Survive millions of years
Survive exposures to radiation & space
Can cause disease
 Inhalation
of Bacillus anthracis endospores
 Contamination of deep puncture wounds with
Clostridium tetani endospores => tetanus
Bacteriology – Endospores


No detectable metabolism
Survive extreme physical and chemical stresses
 UV
light
 Gamma radiation
 Detergents/disinfectants
 Heat
 Pressure
 Drying
Anthrax
Tetanus
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
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