MICROBIOLOGY
VIRUSES
AND BACTERIA
VIRUSES
w “POISONOUS FLUID”
w no nucleus
w no cytoplasm
w no cell structures
w no cell membrane
w extremely small; can’t be seen with a light microscope; only
with an electron microscope
Viruses Cont.
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Some retroviruses cause cancer
w
They convert or transform normal cells to tumor
cells (tumor viruses)
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Plant viruses
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More than 400 viruses that can cause more than
1000 plant diseases
Size and Shape
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Various shapes and sizes
w
typical shape consists
of a head, collar, core, and end plate
w
head: contains a
protein coat (capsid) and nuclear material (either DNA or RNA)
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typical size = 15nm to
200nm
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smaller than most cells
REPRODUCTION
w Needs to be injected into a cell to multiply
w acts like a parasite; but not for food
w atypical reproduction (not sexual or asexual)
w LYTIC CYCLE OR LYSOGENIC CYCLE
CLASSIFICATION
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VIRUSES ARE NOT ALIVE
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THEY DO NOT FIT INTO A KINGDOM
w
THE ARE GROUPED ACCORDING TO SIZE, TYPE, SHAPE
BACTERIA
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Oldest living form discovered around 3.5 billion
years ago
w
placed in the Kingdom
Monera
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unicellular prokaryotes
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there are over 5,000
species that have been identified
CLASSIFICATION
w Based on shape, size, structure, ability to move, how
they eat, and whether they need oxygen
4 classes within the phylum Schizophyta
w Rickettsia: rod shaped or spherical; usually nonmotile
parasites; cause damage to humans (Typhus fever); insect transferred
w
Spirochetae:
cylindrical; motile (rotation/flexing); many cause human disease (syphilis)
w Actinomycota: rod shaped with branched filaments; live
in soils; aerobic and anaerobic; decomposers; can be harmful (tuberculosis and
leprosy); or can be helpful (nasal passage, intestines)
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Eubacteria:
true bacteria, most common
STRUCTURE
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Typical structure contains:
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flagellum (movement)
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capsule (protection)
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cell wall (all
bacteria)
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ribosomes (protein
synthesis)
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plastid (contains
genes)
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nuclear area (DNA)
w
cell membrane
NUTRITION
w Most bacteria are heterotrophic: they use organic food
or compounds from other organisms
w saprophytic: eat dead organisms
w some are symbiotic or parasitic or mutualistic
w some bacteria are autotrophic: make food
w others are chemosynthetic: oxidize inorganic substances
Terms to know
w Heterotrophs:
w energy from organic matter
w Saprophytes:
w live on dead material
w Independent Heterotrophs:
w can live on live or dead organisms
w Dependent Heterotrophs:
w must have food provided by living cells
w Autotrophs:
w energy from inorganic compounds
w Photosynthetic autotrophs:
w energy from the sun
w Chemoautotrophs:
w energy from inorganics
w Mutualism:
w both partners benefit
w Commensulism:
w neither benefit or harm
w Parasitism:
w one member benefits while the other is harmed
RESPIRATION
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Some bacteria need oxygen, others can’t live
with it, while others can live with it or without it
Aerobic Respiration
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Glucose being converted to energy in the
presence of oxygen
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obligate aerobes:
require oxygen
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found in water, soil
ANAEROBIC RESPIRATION
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NO oxygen required
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obligate anaerobes:
have to have no oxygen present
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example: Tetanus
FACULTATIVE BACTERIA
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CAN EITHER LIVE WITH OR WITHOUT OXYGEN
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EXAMPLE: E. COLI
REPRODUCTION & GROWTH
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BINARY FISSION: splitting in two
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REPRODUCTIVE SPORES
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BUDDING
SHAPES OF BACTERIA
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Bacillus - rod shaped
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Coccus - spherical shaped
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Spirallum - spiral shaped
Cynobacteria- blue green bacteria
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Contain chlorophyll and can carry out
photosynthesis
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At one time they were thought to be algae
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prokaryotic and very
small
Importance of Monerans
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Nitrogen fixation:
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bacteria that live on
roots of plants
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nitrogen gas => NH4
=> nitrates => plant amino acids
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amino acids => NH4
=> nitrates in plants => plant a.a.
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Food production:
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dairy products:
buttermilk, cottage cheese, yogurt, cheese
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vinegar
Importance of Monerans cont.
w Food spoilage:
w bacteria cause food to spoil
w low temperatures slows down the process
w freezing stops it
w high temperatures kill most bacteria
w exception: Clostridium botulinum
w anaerobic and basic environment
w extremely deadly
w drying - decreases moisture; kills bacteria
w salting (brining): kills bacteria
w Pasteurization: slow heating
w Radiation
w Alcohol