Prokaryotes

Gen Bio 2

Eukaryotes

Cells with membrane bound organelles and nuclei. Found in multicellular organisms.

Prokaryote

Includes Archea and Bacteria which house singular cell organisms and cells that lack nuclei and membrane bound organelles.

Carl Woese

The creator of the three-domain system to classify organisms in 1977.

Prokaryotic Genomes

• has less DNA than eukaryotic genomes

• consists of circular chromosomes

• Typical genomes are rings of DNA that has no membrane and is located in the nucleoid region

• Some have smaller rings called plasmids

Archaea

• share traits with both eukaryotes & bacteria

• found in both extreme and moderate environments

Prokaryotic Abundance & Size

• estimated population of prokaryotic cells is 4-6×10³^0 cells

• typically measure to be 0.5-5 picometers smaller than eukaryotic cells

• inhabit diverse environments from soil, water to extreme environments

Peptidoglycan

A network of sugar polymers cross-linked by polypeptides

Prokaryotic cells features

• cytoplasm

• cell wall

• cell membrane

• plasmid

• glycocalyx

• (some have flagellum)

• ribosomes

• genophone

• pilus

Pilus

A hair like structure made of repeating proteins called pilin. Used for adhesion, motility, and conjugation.

Genophore

The main long DNA molecule that carries the genetic info in bacteria. Located in the cytoplasm.

Plasmid

A small circular piece of double-stranded DNA found in bacteria that exists and replicated separately from the main bacterial chromosome.

Glycocalyx

• present in different types of bacteria

• a sticky,sugar-rich, outer layer that surrounds the cell wall of many bacteria

• Prevents the cell from drying out

Ribosome

• A tiny molecular machine made of protein and RNA that builds the proteins inside a bacterial cell

• Free floats throughout the cytoplasm

Polysaccharide

A protein layer called a capsule the covers many prokaryotes.

Fimbriae ( Also called Pili)

Long hair like structures that allow them to stick to their substrate or other individuals in a colony.

S3x Pili are longer and allow them to exchange DNA by conjugation.

Gram Staining

A common laboratory test used to divide bacteria into two major groups based on cell wall composition, Gram-positive & Gram negative.

Gram Negative bacteria

Have less peptidoglycan and an outer membrane that can be toxic to other organisms.

more likely to be antibiotic resistant.

Gram Positive

Have more peptidoglycan and a thicker outer membrane which makes it non-toxic and non-resistant to antibiotics

Prokaryotic Motility

• Most motile bacteria propel themselves by their flagella ( structurally different from eukaryotic flagella)

• In heterogeneous environments many bacteria exhibit taxis ( the ability to more toward or away from stimuli)

Heterogeneous environment

A setting made of mixed, dissimilar, or diverse parts rather than uniform elements.

Bacterial Shapes

• coccus ( Cocci/plural), Spherical

• Bacillus, rod-shaped

• Spirillum, spiral shaped

Bacterial Nutrition

• Heterotrophic: Require organic carbon sources

• Autotrophic: Synthesize organic compounds from CO2

• Chemosynthetic: gain energy from oxidizing inorganic compounds

• photosynthetic: Uses light energy to synthesize organic compounds

Asexual Reproduction

Divide through binary fission ( simple cell division )

Transformation

• a type of horizontal gene transfer

• uptakes naked DNA by other competent bacteria and maybe integrated into the genome or existent plasmid.

Transduction

• a type of horizontal gene transfer

• Transfer of DNA by a virus

• Virus activates and rewrites DNA of bacteria to form a new bacteria cell

Conjugation

• A type of horizontal gene transfer

• Transfer of DNA through direct contact with another cell

• a strand of plasmid DNA transfers to the recipient

Life Cycle of Prokaryotes

• Lag: Adaptation to environment

• Log: Exponential growth

• Stationary Phase: Growth rate equals death rate

• Death Phase: nutrient depletion and waste accumlation

• Prokaryotes leads to high mutation rates and genetic diversity

Nutrient Cycling

Prokaryotes help with the decompostiion and nutrient recycling in ecosystems.

Nitrogen Fixation

Cyanobacteria convert atmospheric nitrogen into usable forms for plants.

Symbiotic Relationships

Prokaryotes have relationships with other plants and animals that benefit both of them.

Ex. Nostoc bacteria with hornworts.

Bioremediation

Prokaryotes clean up environmental pollutants.

Prokaryotic Lab Specimen: Spirillum Volutans

• A large, helical bacteria commonly found in stagnant freshwater environments

• known for its distinctive spiral shapes and its role in the microbial ecology of these habitats

• Plays a major role in decompostiion of organic material and indicates water quality

• the presence of spirillum volutans can suggest low oxygen conditions & high organic matter

• measuring 5-8 picometers in diameter

• a bipolar flagella which allows corkscrew motion

• Gram-negative w/ cell wall structure that includes an outer membrane

Bacterial Fermentation

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

Importance of fermentation, preservation, food production

Ex. lactic acid bacteria and yeast

Lactic Acid Fermentation

Carried out by lactic acid bacteria Lactobacillus

converts glucose into lactic acid

examples are yogurt and sauerkraut

Alcoholic Fermentation

Carried out by yeast and some bacteria

Converts glucose into ethanol and carbon dioxide

examples are beer, wine and the rising of bread dough

Acetic Acid Fermentation

Carried out by acetic acid bacteria

converts ethanol into acetic acid

examples vinegar

Cyanobacteria

• photoautotrophs using photosynthesis to generate oxygen

• contain chlorophyll and can fix atmospheric nitrogen (important for plant growth

• has specialized cells like heterocysts and akinetes aid which aid in survival and nitrogen fixation

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