BSCI 124 Lecture Notes
Undergraduate Program in Plant Biology, University of Maryland
LECTURE 15 - Viruses and Prokaryotes
Overview of the classification of organisms - biologists
divide living
organisms into kingdoms as a first step in organizing how they are related
to each other. The classification of kingdoms is based on cell structure
and details of metabolism. For example, plants are a separate kingdom, but
certain plant-like organisms are in other kingdoms due to differences in
cellular organization. New kingdoms have been recently added as scientists
have recognized forms of life that are significantly different than others.
[For a detailed review of the
Plant
Kingdom, see the site maintained by Cardillo & Samuels]
-
Non-living organisms
Virus
-
Technically non-living since they can not self-replicate, thus not a kingdom
-
consists of
just a protein coat for protection and a nucleic acid (RNA or DNA) for
information how to make more copies of the same virus
-
Cellular parasite- uses cell machinery of a host cell to replicate and so
produce more viruses
-
Wide variety of :
EM
pictures: sizes and shapes
-
Cause numerous
diseases of plants,
animals (including humans), bacteria, fungi
-
examples of human viruses:
-
herpes
virus ,
-
hepatitis
virus ,
-
rabies,
-
ebola ,
-emerging epidemics
(video
and pictures of 1995 outbreak in Zaire)
-
influenza
, -recombination between avian(bird) and pig viruses and human viruses
can produce new strains which spread world-wide- e.g. the
Hong
Kong avian flu of Fall 1997 .
Flu fact sheet-
CDC. Dealing with
the flu
-
HIV (AIDS)
(infection process-cartoon
HIV info ).
-
Examples of plant viruses:
-
potyvirus
causing
streaking
,
-
Tobacco Mosaic
Virus causing
mosaic
(mottling) symptoms ,
-
rose mosaic
symptoms ,
-
spots on
fruit
-
Virus-like agents
-
Viroids- Segments of RNA which are not packaged into a protein coat
-
Prion- infectious proteins. e.g.
Mad
Cow Disease, (WHO
FAQ, less
technical description) Kuru, CJ,
-
Living Organisms-two main groups
-
PROKARYOTIC - lack membrane-bounded
organelles
-
Kingdom Eubacteria
(bacteria) - originally classified as plants because they have cell walls
-- Also known as Monera.
-
Kingdom Archaea (or Archaebacteria)
early
evolution of life
-
EUKARYOTIC - membrane-bounded organelles present
-
Summary of the kingdoms of life
-
Kingdom Fungi - molds, mildews, an mushrooms (originally called plants because
they have cell walls and some are "rooted" in the ground)
-
Kingdom Protista - includes algae and slime molds, protozoa (animal-like
protists) - originally considered plants because they have cell wall (not
cellulose) -- Also known as Protoctista
-
Kingdom Plantae
-
Complex multicellular eukaryotes
-
Obtain nutrients by photosynthesis
-
Kingdom Animalia
-
Complex multicellular eukaryotes
-
Obtain nutrients by eating food (ingest)
-
Details on the Prokaryotes (Bacteria and Archaea)
-
Prokaryotic - little internal organization, lack membrane- bounded organelles:
Includes bacteria and archaea (archibacteria)
Features
-
Have cell wall, but not made of cellulose
-
Obtain nutrients in a variety of ways, most through absorption
-
some are photosynthetic, called
cyanobacteria
(previously known as blue-green algae) . Often found in
extreme
environments or as
stromatolitesprehistoric
or modern ) that were
involved in the formation of an oxygen atmosphere on earth. Many are toxic
especially in water
-
Rapid growth through division
of one cell into two
-
produces exact copy of itself - (termed asexual reproduction) -produces very
rapid growth
-
No membranes except plasma membrane
-
No mitochondria, chloroplasts, ER, nucleus
-
No mitosis- simple division
-
Genetic material(1 loop of DNA) but no nuclear membrane surrounding it. No
true sexual reproduction but it does have means of
Genetic
exchange
-
Can survive
millions of
years
-
Eubacteria
(bacteria)
-
B. Size - probably
smallest
living organisms; some about 1/25,000th inch
-
shapes: cocci (spherical),
bacilli (cigar shaped),
spirilli
(helical)
-
Archaea (or Archaebacteria) versus true bacteria (or Eubacteria). Archea
were once thought to be bacteria. However, they have certain features that
are unique or are shared with eukaryotes; thus they have been placed in a
separate kingdom.
-
Archaea are probably found all around us but are unique in being found in
extreme environments
-
high temperature environments:
steam
vents,
deep
ocean vents ,
hot
springs derive energy from
oxidation
of organic compounds with sulfur (S2) rather than
O2
-
high salt environments: salt lakes or evaporating ponds
-
methanogens: derive energy from organic compounds by combining with hydrogen
gas to form methane (e.g.
intestines of animals
and people)
-
Significance of bacteria to humans
-
Beneficial
bacteria (about 90 percent)
-
Nitrogen-fixation in the biosphere (convert atmospheric nitrogen, a very
stable molecule, to useful nitrogen) - 78% atmos N2
nitrogen gas ---> plants ---> animals
-
Decomposition in the biosphere - live on dead organisms, natures recyclers
-
Intestinal
bacteria - supply vitamins ( especially vitamin K)
-
Pathogenic
bacteria-invade host organism, derive nutrition from cells for reproduction
(mechanisms
of how they cause disease- e.g. toxins)
-
Human diseases -
-
pneumonia (1 by bacteria, 1 by virus),
-
Cholera
-
Lyme disease- carried
by ticks (carry
a range of diseases)
-
gonorrhea,
and other sexually
transmitted diseases
-
botulism (food poisoning)
- toxins
-
E. coli
-source of many recent food poisonings-e.g. hamburger
-
Salmonella
of food (e.g. eggs)
-
Campylobacter- bacterial
diarrhea
-
Also some diseases which were not previously thought to be bacterial infections-
e.g. ulcers or heart disease
-
Plant diseases - soft rot (e.g. lettuce in your refrigerator), crown rot
(e.g. that African Violet on your windowsill that is looking limp (about
200 different diseases)
-
diseases you may notice around your yard/garden or kitchen:
bacterial
wilt , spot of
tomatoes
, fire
blight
of apples and pears
-
how to control bacteria to prevent disease
-
heating/cooking (e.g.
in canning)
-
cold temperatures-
limit bacterial growth (e.g. refrigeration)
-
disinfectants-kills most living organisms (e.g. bleach, alcohol, iodine)
-
antibiotics
(e.g.
penicillin
,
tetracycline
, erythromycin ) - drugs that will selectively kill bacteria without
killing the host
(several
different ways of doing this) and so allow treatment of the host.
Movie of bacterial inhibition
by penicillin .
-
However problems are arising with
antibiotic-resistant
bacteria(e.g.
hospital staph infections)
-
Commercial uses
-
Yogurt, sour
cream, sauerkraut; fermentation
-
Genetically-engineered bacteria produce
insulin ,
interferon,
bovine
somatotropin (BSt) and other important medicines
Others Sites of Interest:
Basic
Review
Bacterial
nomenclature
Technical
information on names of bacteria
Images
of Viruses
Baltimore Classification
of Viruses: technical
Classification
of Virus Taxa: Technical
World Data Center for Microorganisms
Glossary of Microbiology
Microbes
in the news
pictures of plant
viruses
FDA food poisoning
information
Biological
Weapons-Scientific American Article
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last updated Feb 10, 1999, Straney