Download Chapter 8 The World of Microbes

Chapter 8 The World of Microbes
Kingdom Monera - The Bacteria
Bio-significanceThe down side:
• Disease of plants → crop loss
• Disease of animals → loss of livestock and herds
• Human disease → cavities to ‘The Plague’
The up side:
• Decomposers – recycle nutrients like carbon, oxygen, and
sulphur back into food chain. Reduces waste (carrion, detritus).
• Nitrogen fixers – make nitrogen available to food chain.
• Fermentation – bread, cheese, yogurt, other milk products.
• Waste-water management.
• Research
MOST BACTERIA ARE EITHER HARMLESS OR BENEFICIAL;
ONLY A (RELATIVELY) SMALL NUMBER ARE PATHOGENIC.
Characteristics:
⇒ Prokaryotic. Single celled
⇒ No membrane-bound organelles. Especially significant is the
lack of a membrane bound nucleus. DNA is therefore freefloating in the cytoplasm.
⇒ Single chromosome, which is normally circular.
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⇒ Most reproduce by asexual reproduction: binary fission (simply
splitting in two) but can exchange DNA with other bacteria
through pili (thin extensions). Some bacteria can even pick up
free floating DNA in the environment ancd incorporate it in their
own genetic material.
⇒ Great metabolic diversity. Bacteria essentially live in every
corner of the globe. Including boiling mud, hot springs, coal
mines, polar ice caps, hot water vents.
Morphology
See handout.
Identification and classification
Shapes
¾ Coccus (pl. cocci) – spherical
¾ Bacillus (pl. bacilli) – rod shaped
¾ Spirilla – spiral shaped
Arrangement
¾ Single
¾ Chains – Strepto
¾ Clusters – Staphylo-
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Biologists group bacteria into one of two Sub-Kingdoms:
¾ Archaebacteria – or “old bacteria” normally live in anaerobic
conditions, high salt/temperature/acidity (idea being that
these were the conditions of early Earth)
¾ Eubacteria – or “true bacteria”…essentially everything else.
However, because there are so many different kinds of bacteria
with so few kinds of shape and arrangement possibilities,
classification is difficult and therefore depends largely on how they
acquire nutrition and the style of respiration they use.
Classification Based On Respiration
⇒ Obligate aerobes – must have oxygen to survive. E.g.
Mycobacterium tuberculosis (Tuberculosis)
⇒ Obligate anaerobes – can only grow in absence of oxygen.
E.g. Clostridium spirillum
⇒ Faculatitive anaerobes – don’t care. Will grow ‘whatever’
Types of Respiration
Aerobic respiration. Bacteria get their energy by turning sugar into
CO2 and water
Anaerobic respiration (Fermentation). Bacteria get their energy by
turning sugar into CO2 and some other organic molecule such as
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Alcohol.
Lactic acid
Acetone
Acetic acid
Methane
Modes of Nutrition
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Heterotrophs – when nutrients are derived from another organism
¾ Parasites – if taken from living organisms. Most diseasecausing bacteria use this.
¾ Saprophytes – if taken from dead and decaying organisms
Autotrophs – when nutrients are made by the bacteria.
⇒ Photosynthesis – when light energy is used to change simple
carbon (like CO2) to a sugar.
⇒ Chemosynthesis – when (because there is no light) chemical
energy is used.
Reproduction
Binary fission - splitting into two equal parts following DNA
duplication. Most common form of replication
Conjugation - A fine tube pilus (pl. pili), which is a cytoplamic
bridge, extends from a donor bacterium to a recipient bacterium of
the same mating type. A small circle of DNA (plasmid) is
transfered and incorporated into recipient DNA. Enteric bacteria
e.g. E.coli and Salmonella.
Endospores - During times of stress, some bacilli bacteria form
protective coats around genetic material. Spore becomes dormant
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and is super resistant to heat…so it is not easily destroyed. When
good conditions occur, bacterium emerges and carries on.
Read p218.
Do p219 Questions (except #3)
or
p220 Case Study
Read p221 Human diseases
Antibiotics and Bacterial Resistance
Some points to ponder:
1) Bacterial resistance is conferred through R-factors which are
proteins which inactivate certain drugs.
2) R-factors are coded for by plasmids and are the result of
mutations(?).
3) Plasmids are swapped freely between bacteria. Recombination
of plasmids creates bacteria with multiple resistances.
4) Antibiotics remove only htose bacteria who do not have the
plasmid for the right R-factor.
5) Removal of competiting bacteria allows resistant bacteria free
access toresources and so they proliferate…Natural Selection.
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Potential result: A bacteria that is resistant to every antibiotic
known to man.
A word: Bardenpho
Kingdom - Protista
Characteristics:
¾ eukaryotic - have membrane bound nucleus and other
organelles
¾ unicellular, microscopic
¾ aquatic and marine environments
Three Groups of Protista
Phytoplankton - (plant-like) producers - autotrophic
{significant contributor to oxygen cycle}
Zooplankton - (animal-like) consumers - heterotrophic
Gymnomycota - (fungal like) ‘rotters’ – saprophytic
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Phytoplankton – plant-like protists
Divided into three groups:
1) Brown algae and diatoms
2) Dinoflagellates
3) Euglenids – oddball organism, has both animal-like and plantlike characteristics.
Zooplankton – animal-like protests (a.k.a. protozoa).
¾ Wide size range 2 µm to 5 cm.
¾ Many different species (st. bacteria)
¾ Normally asexual reproduction (fission) but can form
resting cells (cysts)
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Classification is based on:
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Mode of locomotion
Types of organelles
Life cycle
Mode of reproduction
Nutrition
o Holozoic – engulf food
o Saprozoic – absorb pre-digested or soluble nutrients
¾ Free-living or parasitic
AskJeeves.com>amoebas organisms>#4 Introductory courseware…
Phylum Sarcodina (Amoeba)
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Phylum Ciliaphora (Paramecium)
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Phylum Sporozoa (Plasmodium)
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Gymnocota
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