ProkaryotesProkaryotes

ProkaryotesProkaryotes

• Classification of prokaryotes has Classification of prokaryotes has dramatically changed due to analysis dramatically changed due to analysis of the genomes of various types of of the genomes of various types of cells:cells:

• The description of these organisms as The description of these organisms as members of Kingdom Monera, has members of Kingdom Monera, has been abandoned and replaced with a been abandoned and replaced with a three domain system. These Domains three domain system. These Domains are as follows:are as follows:– Domain Domain BacteriaBacteria– Domain Domain ArchaeaArchaea– Domain Domain EukaryaEukarya

• The domains bacteria and archaea The domains bacteria and archaea contain the prokaryotic organisms.contain the prokaryotic organisms.

• Domain Eukarya include the protists Domain Eukarya include the protists and the other multicellular kingdoms.and the other multicellular kingdoms.

General Bacterial StructureGeneral Bacterial Structure

General CharacteristicsGeneral Characteristics•Bacteria are the smallest "living" organismsBacteria are the smallest "living" organisms•Are prokaryotic cellsAre prokaryotic cells

•Lack NucleusLack Nucleus•DNA is naked. - a single loop - not bound into a DNA is naked. - a single loop - not bound into a chromosome.chromosome.•May contain May contain plasmidsplasmids (small circular fragments of (small circular fragments of DNA)DNA)•Lack membrane-bound organellesLack membrane-bound organelles

•Usually have an outer Cell Wall.Usually have an outer Cell Wall.•Sometimes have an Outer Capsule - These stain red Sometimes have an Outer Capsule - These stain red in a Gram Stain test and are called in a Gram Stain test and are called Gram NegativeGram Negative bacteria.bacteria.•Those without an outer capsule stain blue in the gram Those without an outer capsule stain blue in the gram stain test and are called stain test and are called Gram PositiveGram Positive Bacteria Bacteria

BACTERIAL CLASSIFICATION:BACTERIAL CLASSIFICATION:

• Bacteria are classified generally by 3 Bacteria are classified generally by 3 characteristicscharacteristics

– The bacterial cell shapeThe bacterial cell shape– The bacterial cell arrangementsThe bacterial cell arrangements– Ability to accept a Gram stainAbility to accept a Gram stain

Bacterial Shape:Bacterial Shape:

• Bacteria have 4 Bacteria have 4 basic shapes:basic shapes:– Spherical - Spherical -

coccicocci– Rod-shaped – Rod-shaped –

bacillibacilli– Bent rod Bent rod

shaped - shaped - VibriosVibrios

– Spiral – Spiral – spirillispirilli

Bacterial Arrangement:Bacterial Arrangement:

• Bacteria have 3 basic Bacteria have 3 basic arrangements:arrangements:– Occurring singly = Occurring singly =

““MonoMono” arrangement” arrangement– Occurring in pairs = Occurring in pairs =

““DiploDiplo” arrangement” arrangement– Occurring in long Occurring in long

chains = “chains = “StreptoStrepto” ” arrangementarrangement

– Occurring in clusters Occurring in clusters = “= “StaphloStaphlo” ” arrangementarrangement

Gram Staining:Gram Staining:

• Bacteria can be Bacteria can be categorized by their ability categorized by their ability to accept a gram stain.to accept a gram stain.– Bacteria are exposed to Bacteria are exposed to

several staining agents; several staining agents; Crystal Violet, Gram’s Crystal Violet, Gram’s Iodine, and safranine.Iodine, and safranine.• If the bacteria possesses a cell If the bacteria possesses a cell

capsule, it will retain a pink capsule, it will retain a pink color. This is referred as to a color. This is referred as to a ““Gram NegativeGram Negative” bacteria” bacteria

• If the bacteria lacks a cell If the bacteria lacks a cell capsule it will retain a blue capsule it will retain a blue color. This is referred to as a color. This is referred to as a ““Gram PositiveGram Positive” bacteria” bacteria

Gram Negative BacteriaGram Negative Bacteria

Gram Positive BacteriaGram Positive Bacteria

How Bacteria obtain energy:How Bacteria obtain energy:

• Two major categories:Two major categories:– AutotrophsAutotrophs - Make their own energy - 2 types - Make their own energy - 2 types

• Phototrophic autotrophsPhototrophic autotrophs - Get energy from sunlight - Get energy from sunlight• Chemotrophic autotrophsChemotrophic autotrophs - Get energy from inorganic - Get energy from inorganic

molecules (eg. Sulfides)molecules (eg. Sulfides)

– HeterotrophsHeterotrophs - Energy obtained from other - Energy obtained from other organismsorganisms• Chemotrophic heterotrophsChemotrophic heterotrophs - obtain energy by - obtain energy by

dissolving/absorbing organic materialdissolving/absorbing organic material• Phototrophic heterotrophsPhototrophic heterotrophs - meet some energy needs - meet some energy needs

from photosynthesis, but must absorb organic from photosynthesis, but must absorb organic compounds.compounds.

Bacterial RespirationBacterial Respiration

3 major categories3 major categories

• Obligate aerobesObligate aerobes. - Must have O. - Must have O22 in in order to liveorder to live

• Obligate anaerobesObligate anaerobes - Must live in - Must live in an Oan O22 free environment free environment

• Facultative anaerobesFacultative anaerobes - Can live - Can live with or without Owith or without O22..

Bacterial Reproduction:Bacterial Reproduction:

• Bacteria reproduce through Bacteria reproduce through binary binary fissionfission..

• Can engage in primitive sexual Can engage in primitive sexual reproduction called reproduction called conjugationconjugation..– A bridge is formed between 2 bacteriaA bridge is formed between 2 bacteria– PlasmidsPlasmids are shared across bridge, thus are shared across bridge, thus

exchanging genetic information.exchanging genetic information.– In times of harsh conditions, bacteria can form In times of harsh conditions, bacteria can form

endosporesendospores, to encapsulate themselves in a , to encapsulate themselves in a dormant state, until conditions improve.dormant state, until conditions improve.

MotilityMotility

• Some Some bacteria are bacteria are motile - can motile - can move by move by either either thrashing, thrashing, secreting secreting lubricating lubricating secretions or secretions or through use through use of a of a flagellumflagellum

ArchaeaArchaeaEvolutionary

Relationships• Analysis of

molecules found within the cells suggests that eukaryotes are more closely related to archaea than to bacteria.

Major Groups of ArchaeaMajor Groups of Archaea

• Three major groups of archaea are found in extreme habitats.– Methanogens are found in anaerobic

environments.such as marshes and in the intestinal tracts of animals. They produce methane as a result of cellular respiration.

– Halophiles are found in environments with high salt concentration such as the great salt lake or soil with a high salt concentration.

– Thermoacidophiles live in hot, acidic environments such as hot springs and hydrothermal vents.