Chapter 18 – Viruses and Bacteria

 

Bacteria – simplest living organisms

 

Viruses – simplest non-living things

 

                                    VIRUSES

 

Def. – a biological particle composed of genetic material and protein

-         contain either DNA or RNA but not both

-         genetic material encased in a capsid – made of proteins

-         obligate intracellular parasite – have to use host’s system’s to reproduce

-         * highly host specific

 

Virulent – causes serious diseases

-         causes host’s cells to Lyse – to break open

 

Temporate – do not cause immediate disease – put their DNA into host DNA

 

Variolation – exposing healthy people to sick people’s scabs

 

Vaccination – exposing people to harmless or dead versions of a serious virus

 

Tissue Culture – growing living cells in a controlled environment.  (Viral research)

 

Serology – the study of biological fluids

-         can determine an organism’s antibody response to a virus

 

Electrophoresis – separating molecules by their electrical charge

-         used to study virus proteins

 

Icosahedron – 20 sided shape

 

Capsid – protein sheath surrounding DNA or RNA

 

****Viruses contain only DNA or RNA, but never both.****

 

Viroids – particles smaller and simpler than viruses that cause diseases.

 

Prion – causes diseases with long incubations

-         Kuru – degenerative brain disease (nerves) – get it by touching the brains of an infected person

 

Bacteriophages – viruses that infect bacteria -T group phages

                       (insert picture)

 

 

Lytic Cycle – reproductive process of virulent viruses

 

Five (5) Phases of the Lytic Cycle (1-2 day cycle)

 

1.      Adsorption – virus attaches to host at receptor sites

2.      Entry – T4 releases an enzyme that breaks down the host cell wall and injects it’s genetic material into host

3.      Replication – viral DNA takes over and manufactures itself.

4.      Release – T4 releases another enzyme that eats the bacterial wall from the inside (Lyses) and new virus is released.

 

(insert drawings)

 

 

 

Lysogenic Cycle – for temportate viruses

 

1.      & 2. Temperate virus enters same as T4 steps 1 & 2.

3.       DNA attaches to host DNA by prophage – short DNA segment of the virus.

4.      Whenever host cell divides or grows it stimulates the virus DNA segments also.

 

 

Transduction – when a temporate virus takes part of the host’s DNA with it when it

leaves and introduces the first host’s DNA into a 2nd host.  Therefore, causing a new genome therefore, a new phenotype.

 

Evolution of Viruses – no fossil history

 

 

 

BACTERIA

 

Characteristics:

-         prokaryotes

-         unicellular

-         no membrane bound organelles

-         microscopic

-         simplest living thing

 

I.                    Ancient Bacteria

 

A.     Kingdom Archaebacteria – live in places similar to the environment in early earth’s time.

 

3 Phyla

 

1.      Phylum Aphragmabacteria

(Thermoacidophiles) – love extremely hot and acidic habitats (hot springs, Old Faithful)

 

2.      Phylum Halobacteria (halophiles) – love very salty water (dead Sea, Great Salt Lake)

 

3.      Phylum Methanocreatrices (Methanogens) – cannot live in oxygen environments (sewage ponds, cattle digestive tracts)

 

 

II.                 True or Modern Bacteria

 

A.     Kingdom Eubacteria

-         you are most familiar with these types of bacteria

-         live freely in soil, water, and you

 

Reactions to Antibiotics

 

-         gram test – bacterial test to determine if a bacteria is treatable with antibiotics or not.

-         (+) – look purple under the microscope * can treat with antibiotics

-         (-) – look pink under microscope * cannot treat with antibiotics

 

5 Phyla

 

1.      Phylum Actinobacteria

-         rod shaped

-         gram positive

-         cause diseases

-         most antibiotics made using these bacteria

 

2.      Phylum Omnibacteria – salmonella

-         causes food poisoning – death

-         gram positive

 

 

3.      Phylum Spirochaetae – spirochaetes

Treponema

-         spiral shaped

-         move by using a rotating flagella

-         most STD’s – syphilis

-         Lyme disease – carried by deer ticks

 

4.      Phylum Chloroxybacteria (green bacteria)

Prochloron

-         photosynthetic

-         live in symbiosis with marine chordates

 

5.      Phylum Cyanobacteria (blue-green “algae”)

Nostoc

-         have some plant traits

-         have chlorophyll

-         photosynthetic

-         produce oxygen

-         “bloom” in water (can turn water colors when in abundance)

-         plants may have evolved from this group

 

 

 

Nutrition types:

1.      heterotrophs – use other organic materials for food

a.       saprobes – feed on dead and decaying organisms (decomposers)

b.      parasitic – absorb a host’s nutrients that have been predigested for them.

 

2.      autotrophs – make own energy

a.       photoautotrophs – obtain energy from sunlight; photosynthesize; contain chlorophyll

b.      chemoautotrophs – obtain energy by breaking down inorganic substances (nitrogen, sulfur)

 

 

 

Respiration types:

 

1.      Obligate anaerobes – bacteria that cannot live in oxygen.

 

2.      Facultative anaerobes – bacteria that can live either with or without oxygen in their environment.

 

3.      Obligate aerobes – bacteria that must have oxygen in their environment to live.

 

 

Reproduction:

 

1.      binary fission – asexual; divides in half; genetic clones for offspring

2.      conjugation – sexual; transfer genetic material through a bridge-like structure called Pili; genetic variation in offspring

 

Toxin Production:

 

-         Pathogen – an organism that causes diseases – produces toxins

-         Toxin – poisonous substance that interrupts your metabolism – if strong enough will cause death

1.      endotoxins – found inside cell walls: gram (-)

2.      exotoxins – bacterial bi-products excreted into area surrounding the bacteria; most potent poisons known (botulism, tetanus)

 

 

 

Antibiotics – chemicals that can inhibit growth of some bacteria

-         they may be natural or man-made

-         2 negative side affects

a.       bacteria can build up a resistance to the antibiotic

b.      antibiotics kill the good bacteria along with the bad bacteria

 

Alex Fleming – discovered 1st antibiotic – Pennicillin

 

 

Structure of Bacteria:

Six most common shapes

1.      Cocci – spherical

2.      Bacilli – rod

3.      Helices – spirals

4.      Staphylo – clusters

5.      Strepto – chains

6.      Diplo – pairs

 

DNA – circular; floats freely in cytoplasm

 

Capsid – protective protein covering

 

Flagella – hair-like structure used for locomotion “rotating” motion

 

Endospores – tough outer layer that forms when habitat becomes unfriendly (drought, freeze, fire, flood)

-         allows bacteria to go dormant for long periods of time (Anthrax – can be dormant for 60 + years

-         2 structures that help bacteria stick to surfaces:

1.      pili – fibers

2.      glycocalyx – sticky sugar “glue”

 

Best growth conditions:

-         warm – 78 to 100 degrees

-         moist

-         dark

-         food supply

 

Harmful effects of Bacteria:

1.      spoils food – food poisoning, botulism, salmonella

2.      causes tooth decay

3.      causes diseases

4.      water pollution

 

Benefits of Bacteria:

1.      major decomposers

2.      fermentation

3.      food products – cheese, butter, vinegar, yogart

4.      aids digestion of some animals – cows, termites

5.      antibiotics produced – penicillin

6.      genetic engineering