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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
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
Not membrane bound
Smaller than Eukaryotic
Barrier againstphagocytosis
Hairlike protein extensionsAttach/communicate withOther cells
DNA outside chromosomeReplicate independentlyPass info via pilus
Mobility
FEW BACTERIA HAVE ABILITY TO PRODUCE ENDOSPORESPersists in variable environment
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 kills by inhibiting a step in synthesis
of cell wall 2 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 bacteriaGram's iodine - fixes the stain in gram positive bacteriaEthanol or acetone - washes the stain from gram negative bacteriaSafranin - counterstain, will re-stain 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
Cocci Staphylococcus species Streptococci
RodsC: Coyrnbacterium
pseudotuberculosisL: Listeria monocytogenesE: Erysipelothrix rhusiopathiaeA: Arcanobacterium pyogenesR: 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 Pseudomonas aeruginosa Pasteurella multocida Moraxella bovis Anaerobes: Bacteroides,
fusobacterium Campylobacter: spiral
twisted Rickettsia and Chlamydia
GRAM POSITIVE GRAM NEGATIVE
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
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
No detectable metabolism Survive extreme physical and chemical
stresses UV light Gamma radiation Detergents/disinfectants Heat Pressure Drying
Bacteriology – Endospores
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
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
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 media Specific nutrients added or deficient or
antibiotics added Used to ID specific organisms
Bacterial Reproduction
References
http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_Interpreting_Plates.shtml
http://www.vetmed.ucdavis.edu/whc/pdfs/necropsy.pdf
http://www.vetmed.wisc.edu/pbs/courses/bact/labmanual/labmanual.html
http://pathmicro.med.sc.edu/fox/enterobact.htm