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