Prokaryotes

Bio 2 exam

Prokaryotes

Include kingdomes Archaea and Bacteria which have no nuclei and membrane bound organelles.

Eukaryotes

Have membrane bound organelles, nuclei, and can be multicellular.

Prokaryotic Genome

A ring of DNA that does not have a membrane holding it together and is located in the nucleoid region.

Most of the genome consists of circular chromosomes

Has less DNA than a eukaryotic genome

Plasmids

Common in some species of bacteria, they are small rings of DNA floating around the cell

Archaea

A domain that consists of single-celled prokaryotic organisms that thrive in extreme environments. Linked together by lipids in their cell membranes

Prokaryotic Size and Abundance

Prokaryotes inhabit diverse environments from soil, water, and extreme conditions.

There are around 4-6×10³0 cells around the world

Typically measure 0.5-5 um in diameter and are smaller than eukaryotic cells

Prokaryotic cell walls

Cell walls maintains the structure of the cell while also providing physical protection and prevents bursting in hypotonic environments

Bacterial cell walls are made of peptidoglycan

Peptidoglycan

A network of sugar polymers cross-linked by polypeptides found in bacterial cell walls

Prokaryotic cell structure

Capsule

A polysaccharide/protein layers covers many prokaryotes

Fimbriae/ Pili

Long hair like tendrils that allow prokaryotes to sick to others or surfaces

Shorter pili are known as s3x pili and allow prokaryotes to exchange DNA by conjugation

Gram Staining

A test that scientists use to see if a bacterial species is toxic by testing the cell wall compostition

Gram-negative bacteria= less peptidoglycan and an outer membrane that is toxic and antibiotic resistant

Gram-positive bacteria= more peptidoglycan and aren’t antibiotic resistant

Antibiotics target cell walls and break them down causing cell lysis

Motility

Bacteria propel themselves by a flagella that is different from eukaryotic flagellas

In heterogeneous environments many bacteria exhibit taxis

Taxis is the ability to move towards or away from stimuli

Internal Organization of Prokaryotes

Prokaryotes lack complex compartmentalization, but some do have specialized membranes that perform metabolic functions

Bacterial shapes

Three shapes:

Coccus/Cocci: spherical

Bacillus= Rod shapes

Spirillum= spiral or curved

Heterotrophic

Require organic carbon sources

Autotrophic

Synthesize organic compounds from CO2

Chemosynthetic

Gain energy from oxidizing inorganic compounds

Photosynthetic

Use light energy to synthesize organic compounds

Asexual reproduction in prokaryotes

Mainly through binary fission which is simple cell division

Horizontal Gene Transfer

Transformation is the uptake of naked DNA

Horizontal Gene Transfer Transduction

Transfer of DNA by a virus

Horizontal Gene Transfer Conjugation

The transfer of DNA through direct contact

Life History of Prokaryotes

Prokaryotes have rapid reproduction rates which lead to high mutation rates and genetic diversity

Life Cycle:

Lag Phase: Adaptation to environment

Log Phase: Exponential growth

Stationary Phase: Growth rate equals death rate

Death Phase: Nutrient depletion and waste accumulation

Ecological Significance of Prokaryotes

Nutrient Cycling: Decomposition and nutrient recycling in ecosystems

Nitrogen Fixation: Cyanobacteria convert atmospheric nitrogen into usable forms for plants

Symbiotic relationships: lots of relationships with plants that benefit both parties

Ex) Nostoc with hornworts and animals

Bioremediation: Use of bacteria to clean up environmental pollutants

Spirillum Volutans

A large helical bacterium commonly found in stagnant freshwater environments

Known for its spiral shape and its role in its habitat.

Plays a role in decomposition and indicates water quality. Its presence suggests low oxygen conditions and high organic matter content

5-8 um in diameter

Has a bipolar flagellum which allows it to move in a corkscrew motion

Gram negative with a cell wall with an outer membrane

Helps with food production, preservation, health benefits

Bacterial fermentation

A metabolic process that converts sugars to acids, gases, or alcohol in the absence of oxygen

Lactic acid bacteria and yeast are key players in fermentation

Lactic Acid Fermentation

Carried out by lactic acid bacteria called Lactobacillus converts glucose into lactic acid

Alcoholic Fermentation

Converts glucose into ethanol and carbon dioxide

Cyanobacteria

Photoautotrophs using photosynthesis to generate oxygen

Contain chlorophyll and can fix atmospheric nitrogen important to plant

specialized cells like heterocyst and akinetes aid in nitrogen fixation and survival

Cyanobacteria and Their Importance

Photoautotrophic: Generate oxygen through photosynthesis and contains pigments with phycocyanin and chlorophyll

Heterocysts

Nitrogen fixation

Akinetes

Allows for survival in adverse conditions

Gloeocapsa

Genus of cyanobacteria known and blue green algae found in aquatic habitats and moist terrestrial locations known for its gelatinous sheath and colonial organization.

Spherical and often form colonies with gelatinous sheath which provides protection and helps the cells adhere to each other.

Reproduce asexually through binary fission

Communally found in freshwater and marine environments as well as wet stony surfaces

Plays a role in nitrogen fixation which is crucial for nutrient cycling in ecosystems

Gelatinous Sheath function protects from desiccation and UV radiation while adhering to surfaces

Photosynthesis occurs in thylakoids which are disperse throughout the cytoplasm

Contributes to primary production in aquatic ecosystems and is involved in nitrogen fixation making nitrogen available

Oscillatoria

A genus of filamentous cyanobacteria

named for oscillating movement

found in a variety of aquatic and moist terrestrial environments

Forms long unbranched filaments

Made of a series of cells that slide back and forth

Reproduces asexually by fragmentation filaments break down into smaller pieces each one can grow into a new filament

Freshwater, ponds, lakes, and streams found on wet soil and rocks

Plays a role in primary production and nutrient cycling in its habitats

Movement helps organism to find optimal light conditions for photosynthesis

Uses photosynthesis using chlorophyll A and phycobiliproteins

Photosynthetic pigments are located thylakoids which are evenly distributed within the cell

Helps with oxygenation of water bodies through photosynthesis

Nostoc

Cyanobacteria known for filamentous cells and colonies

Symbiotic relationships with plants and fungi

Forms of bead-like chains called trichomes within a gelatinous sheath spherical or oval

Reproduction by binary fission and fragmentation

Forms specialized cells called heterocyst for nitrogen fixation

Found in freshwater lakes ponds moist soils and symbiotic relationships with plants

Important for primary production and nitrogen cycling

Chlorophyll A and phycobiliproteins for photosynthesis Thylakoids distributed throughout the cell for light absorption