BACTERIA

Bacteria are Prokaryotes Prokaryotes were the initial inhabitants

of Earth and today are found almost everywhere

Have no nuclear membrane nor membrane-enclosed organelles

Inside the cell is one large circular strand of DNA or RNA

Bacteria In General: Are the oldest and most abundant living

organisms on Earth All share basic structures but are diverse

in cell shape and nutritional patterns Affect humans in various ways: cause

disease, spoil foods, can be resistant to antibiotics

Fix nitrogen for plants, decompose organic matter, manage hazardous waste, aid animal digestion, help create dairy products

General Structure of Bacteria:

Further Investigation...

http://www.cellsalive.com/cells/bactcell.htm

Archaebacteria: Oldest of all life forms Hypothesized that all life kingdoms

descended from ancestors of this group! Organisms in this taxon possess:

-cell walls-single chromosome-unicellular in nature

Over half the genes in archaebacteria differ from those of eubacteria

3 Main Orders of Archaebacteria:

METHANOGENS-live in oxygen free

places,such as animal

intestines

3 Main Orders of Archaebacteria:

HALOPHILES-salt loving-found in the Dead

Sea

3 Main Orders of Archaebacteria:EXTREME

THERMOPHILES

-live in hot, acidic environments such as hot springs

Eubacteria Most successful of prokaryotes Organisms belonging to this taxon

possess:-cell walls-single chromosome-unicellular in nature

Basic Bacteria Structure: Both archaebacteria and eubacteria are

classified according to:

1. Cell Shape2. Gram Stain3. Nutrition4. Respiration

1. Cell Shape

Bacteria cell shapes come in 3 basic forms:

1. Round – coccus2. Rod – bacillus3. Spiral - spirillum

1. Cell Shape Cocci that live as separate

cells = monococci. Cocci live in pairs = diplococci Cocci live in linear chains =

streptochocci. Cocci live in grapelike clusters

= staphylococci Bacilli also exists as single,

pairs or chains or random attachments

Spiral bacteria exist only as single cells

2. Gram Stain Gram staining is a differential staining

procedure that allows the categorization of bacteria into 2 groups based on their ability to retain a violet stain colour

2 groups: Gram Positive OR Gram Negative

(purple colour) (pink colour)

Differences in Gram Staining Gram-positive

organisms are able to retain the crystal violet stain because of the high amount of peptidoglycan in the cell wall.

Gram-positive cell walls typically lack the outer membrane found in Gram-negative bacteria.

3. Nutrition All cells need energy and a source of

carbon for cellular respiration. major energy source

light= photosynthetic bacteria Inorganic compounds = chemosynthetic

bacteria

Photoautotrophs photoheterotrophs chemoautotrophs chemoheterotrophs

3. NutritionPhotoautotrophs: -can synthesize their own

organic compounds from sunlight

-Cyanobacteria (a.k.a. Blue green algae)

-forms blooms in polluted water due to nitrate and phosphate run-off into the water

-use up oxygen in lakes/ponds/water source

Bloom of Blue-Green Algae:

3. NutritionChemoautotrophs:-obtain energy by breaking apart chemical

bonds in inorganic compounds such as hydrogen sulphide and ammonia

Chemoheterotrophs:-live everywhere-some are parasites and live off hosts-some are saprobes and consume

decomposing hosts

4. Respiration All living things must carry out cellular

respiration to receive energy for life’s functions Bacteria differ in whether or not they need

oxygen Bacterial respiration falls into 2 basic

categories:1. Aerobes

-cellular respiration involves oxygen to produce energy from food that is broken down-obligate aerobes absolutely need oxygen for survival

4. Respiration

2. Anaerobes-bacteria that carry out cellular respiration in an oxygen-free environment-if the presence of oxygen kills these organisms, they are called obligate anaerobes

4. RespirationExample: obligate

anaerobe = soil bacterium called Clostridium botulinum that produces toxins that can cause an extreme form of food poisoning called botulism

3. Facultative Anaerobes: can survive in either environment

Bacterial ReproductionDepending on environmental conditions,

bacteria can reproduce in a variety of manners:

1. Under favourable conditions2. Under unfavourable conditions3. Under extreme conditions

Under Favourable Conditions: All bacteria use binary fission (asexual

reproduction) under ideal conditions Produce EXACT copies of themselves: parent

cell divides into 2 identical offspring Can divide every 15-20 minutes In 12 hours there is 10 to 100 million bacteria! Genetic mutations occur which increase their

diversity and ability to survive Due to fast reproduction rate bacteria mutate

often – 2000/day If the mutation is favourable then it spreads

through the population quickly

Binary Fission

Under Unfavourable Conditions Will reproduce using conjugation if conditions begin

to fail (lack of food, heat, dessication –drying out- or space)

2 bacteria cells connect to each other by long protein bridges called a pilus between them

1 cell transfers a copy of their plasmid (smaller ring of DNA with fewer genes than chromosomes) to the other cell

The bacteria that received this plasmid now has a different genetic make up and this thereby increases their chances of survival

Example: bacteria become resistant to antibiotics

Conjugation

Under Extreme Conditions: Bacteria form structures called spores – one such

is called an endospore Many gram positive bacteria form these spores Endospore: bacteria produces a thick wall

around DNA and cytoplasm This enables them to remain dormant for long

periods (months) until conditions are once again favourable

So, endospores do not metabolize or reproduce but simply exist until conditions become favourable

Endospores

Endospores Example of Clostridium

bacteria with characteristic drumstick-shaped endospore-producing cells.

The dark rod-shaped cells are vegetative cells.

The clear ovals are endospores, and the objects consisting of both dark rod and clear oval are vegetative cells producing endospores.