BacteriaBiology 342

Prokaryotes and Eukaryotes

Prokaryotes – single celled organisms lacking a membrane bound nucleus or organelles. All their DNA and proteins are together in the cytoplasm enclosed by the cell membrane.

Eukaryotes – some single celled, but mostly multicellular organisms with DNA enclosed in a membrane – the nucleus, and having organelles such as chloroplasts, mitochondria, Golgi bodies.

Interesting facts

Two prokaryote Domains: Archaea and Bacteria

Prokaryotes are extremely promiscuous with their DNA – sequences are exchanged among different species and even different Kingdoms

Species concept (BSC) breaks down with bacteria

Bacteria diversity is more like genetic clusters or groups which are often termed genospecies

Archaea (Archaebacteria) and Bacteria (Eubacteria)

Archaea Cell wall: single

compound Spores: absent – no

dormancy Habitat: extremely harsh

environments such as hot springs, salt lakes, oceans, and within the guts of ruminants and including humans

Few or no pathogens

Bacteria Cell wall: multiple

compounds Spores: present – can

remain dormant for years Habitat: ubiquitous –

found everyplace on earth from hot springs, lakes, streams, oceans, soil, within plants and animals

A large variety of pathogenic types

Prokaryote Cell

Size

Bacteria Classification

The Gram stain, a crystal violet dye separates two groups of bacteria based on structural differences of their cell wall.

Gram positive bacteria retain the dye color and are violet or purple

Gram negative bacteria resist the dye color and are red or pink.

Gram Positive Bacteria showing the dark violet or purple color

Gram Negative Bacteria showing the red or pinkish color

Gram Negative vs. Gram Positive

Gram (–) and Gram (+) Bacteria

Gram negative Stain: red or pink Outer membrane:

present Flagella: 4 rings in basal

body Toxins: endotoxins Drying: low resistance Antibody: high resistance Pathogenicity: high (90%

of pathogenic bacteria)

Gram positive Stain: dark violet or

purple Outer membrane: absent Flagella: 2 rings in basal

body Toxins: exotoxins Drying: high resistance Antibody: low resistance

– more susceptible Pathogenicity: most are

not pathogenic

Flagellum with Basal Body Rings

Bacterial Shapes

Bacilli (rod-shaped)

Cocci (sphere-shaped)

Spiral (corkscrew-shaped)

Bacteriophages

Viruses infecting a bacteria seen here in a electro-micrograph and as plague forming units on a agar plate.

Timeline of Awareness

Van Leeuwenhoek built microscopes and discovered one-celled organisms back in the 1670s. Leeuwenhoek provided science with the knowledge that our world is teeming with small single-celled life.

Louis Pasteur demonstrated that microorganisms could be grown in broth in sealed tubes – but boiled broth did not grow organisms = Pasteurization ~ 1860s.

Robert Koch demonstrated that the disease Anthrax was caused by a bacteria ~ 1860s.

Germ theory developed in the 1870s.

Bacterial Disease Examples

Bubonic Plague – Yersinia pestis killed millions of humans, est. 60% of European population

E coli O157:H7 – Escherichia coli stain that can cause severe anemia, kidney failure and death

Anthrax – Bacillus anthracis produces lasting spores that lethal is breathed or consumed typically in contaminated meat

MRSA – Methicillin-resistant Staphylococcus aureus developed resistance to many antibiotics -widespread in hospitals and clinics

TB – Mycobacterium tuberculosis – attacks lungs, kidneys, spine, and brain – most often fatal.

Bacterial Diseases

Cholera – Vibrio cholerae infects the intestine through feces contaminated water and food, causes diarrhea, dehydration and death

Lyme disease – Borrelia burgdorferi, a tick-borne spirochete causes erythema migrans, arthritis, heart, and nerve damage.

Tetanus – Clostridium tetani enters body through a break in the skin – puncture wound – a toxin disrupts muscle contraction

Gonorrhea – Neisseria gonorrhoeae, a sexually transmitted disease causing inflammation in pelvic and epididymis.

Anthrax, Bacillus anthracis

Transmission: Contact of dormant endospores – open skin, inhaled, or ingested.

Endospores survive (decades to centuries) are found in soil on every continent including Antarctica

Hosts are most commonly wild and domestic herbivores – Carnivores become infected consuming infected prey

Symptoms: pulmonary – flu-like, pneumonia, respiratory collapse (10,000 spores lethal); gastrointestinal – vomit blood, diarrhea, lesions in mouth and throat; Cutaneous – black eschar

Anthrax – Bacillus anthracis

Cutaneous (“skin”) anthrax ulcer with black center (anthracis=Greek anthrakis=“coal”Starts as a boil – ulcer with black center (eschar) then an expanding necrotic ulcer – toxemia - death

Anthrax Weapons

Biological weapons developed in Russia and US. Concentrated spores into powder used as aerosol

Russian accident or experiment

Bioterrorism in US (2001) – concentrated spores placed into envelopes and mailed to news media and two Democratic senators – 22 infected, 5 died. Postal service now scans all mail for anthrax

Lyme erythema migrans – Borrelia burgdorferi

Plague bubo – Yersinia pestis

Tetanus – Clostridium tetani

Anaerobic bacteria produces endospores which remain in soil for decades – spores are ubiquitous world wide

Spores reside in the intestines of horses, sheep, cattle, dogs, cats, rats, even chickens and enter soil via manure

People become infected through a puncture wound or through a cut in the skin

2013 ~ 60,000 deaths world wide; 1990 350,000 deaths

Tetanus vaccine

Tetanus (lockjaw)

Tetanus (lockjaw) is caused by the bacterial toxin which interferes with muscle contractions.

Muscle spasms start in the jaw then progress through entire body – lasting minutes and occur frequently for weeks to months beginning 3-20 days post exposure

Spasms can be so severe as to cause hyper extension of the body in to a arching position called opisthotonos –the spasms often cause bone fractures

Mortality with treatment runs ~ 10%.