2.2 Prokaryotes

Pro= Before

Kernal= Nucleus

  • Prokaryotes- before Nucleus

    • Single-celled organism that lacks a nucleus and membrane-bound organelles

  • Oldest structurally simplest, and most abundant forms of life

  • abundant for over a billion years before eukaryotes

  • 90-99% unknown and undescribed

  • Less than 1% cause disease

  • Fall into 2 domain

    • Bacteria (also known as Eubacteria)

    • Archea (formally called Archaebacteria)

LUCA - Last Universal Common Ancestor

  • Made of cells

  • Used DNA/RNA to code genetic information

  • Bacteria-like

Prokaryotic Evolution

  • Hash condiction of early Earth

    • Protective environments

    • Extremophiles (could survive in extreme settings)

  • First life forms on Earth

    • Microbial mat fossils date to 3.5 byo

    • Energy from chemicals at hydrothermal vents

Prokaryotes are NOT a monophyletic group

Archean are more closely related to us than to bacteria

Prokayoti is a characteristic or trait, not a taxa

Extremophiles (make flash cards)

  • Acidophiles: pH 3 or below

  • Alkaliphiles: pH 9 or higher

  • Thermophiles: Tempature 60-80 ºC (140-176 ºF)

  • Hyperthermophiles: Tempature 80-122 ºC (176-250 ºF)

  • Psychrophiles: Tempature -15-10 ºC (5-50 ºF) or lower

  • Halophiles: Salt concentration of at least 0.2M

  • Osmoplies: High sugar concentration

  • Hypolith: Low Humidity/ water

Characteristics of All Cells (Eukaryotic & Prokaryotic)

  1. Plasma membrane

  2. Cytoplasm

  3. DNA Genome

  4. Ribosomes

Prokaryotic Characteristics

All

  • Unicellular, but can form communities

  • Single cicrular, doule-stranded DNA chromosome (No nuclous- no membrane)

  • Nuclieoid: Region (no envelope) of the cell that contains genome

  • Cell wall & plasma membrane

  • Ribosomes

Some

  • Capsule (third external layer)

  • Flagellum (tail they use to move around)

  • Pili (Used to adhere to things)

Shapes

  • Cocci- circular

  • Bacili - rod-shape

  • Spirlli - spiral shape

Reproduction

  • Asexually only, by binary fission, do not undergo mitosis

    • Chromosomes are replicated

    • Cell pinches inward

    • Two clone cells are created

  • Vertical gene transfer: Parent to offspring

  • Horizontal gene transfer: transfer of genetic material from an organism to another organism, not its offspring

    • can occur between different species

    • Responsible for most genetic variation rather than mutation

    • Can cause large-scale changes in bacterial genome

    • If transferred genes do not provide a selective advantage they are always lost by deletion

Prokaryotic Genetics

A. Transformation: The cell takes up prokaryotic DNA directly from the environment. The DNA may remain separate as plasmid DNA or be incorporated into the host genome.

B. Transduction: a bacteriophage injects DNA into the cell that contains a small fragment of DNA from a different prokaryote

C. Conjugation: DNA is transferred from one cell to another via a pilus that connects the two cells (most common form)

Prokaryotic Energy Classifications

Energy source used to generate ATP

  • Phototrophs: Sunlight

    • Photoorganotrophs (organic)

    • Photolithotrophs (inorganic)

  • Chemotrophs: Chemical compound

    • Chemoorgoniotroph (organic)

    • Chemolithotroph (inorganic)

Carbon source

  • Autotrophs: Inorganic compounds such as CO2

  • Heterotrophs: organic compounds

Prokaryotic Energy Classifications

Oxygen Requirements

  • Obligate aerobes: require oxygen for ATP Production via cellular respiration

  • Obligate anaerobes: Oxygen is toxic; use fermentation or anaerobes respiration with inorganic molecules like SO4, NO3

    • Gut bacteria

  • Facultative anaerobes: Can produce ATP with or without (fermentation) Oxygen

Archaea & Bacteria

  • Prokaryotes is not a taxonomic term (Is a trait or characteristic)

  • Bacteria and Archaea are both prokaryotes but different enough to be placed in separate domains

  • An ancestor of modern Archaea is believed to have given rise to Eukarya, the third domain of life

Plasma Membrane

  • Archea: Branched with ether bonds

  • Bacteria: Unbranded with ester bonds

Cell Wall

  • Archaea: Composed of polysaccharides (Long chains of sugar)

  • Bacteria: Composed of peptidoglycan

Gene expression

  • Archaea: Transcription and translation are more similar to those of eukaryotes; enzymes are also similar

Pathogenetic

  • Archaea: none are pathogenic to humans (infect humans)

  • Bacteria: Are infectious

Classification of Bacteria

  • Gram-positive and Gram-negative

  • Both groups have cell walls composed of peptidoglycan

    • Gram-positive bacteria: The wall is thick

    • Gram-negative bacteria: The wall is thin

Domain Bacteria

  1. Proteobactiera: Gram-negative: eukaryotic mitochondria are though to be derived from this group

  2. Chlamydias: obligate intracellular parasites of animal cells; cell walls lack peptidoglycan

  3. Spirochetes: spiral-shapec cells; mostly anaerobic

  4. Cynobacteria: photosyntheic: eukaryotic chloroplasts are thought to be derived from this grou

  5. Gram-positive bacteria: thick cell wall

Domain Archaea

  1. Euryarchaeota: methangens & halobacteria

  2. Crenachaeota: carbon fixation & sulfur-dependent/ thermophilic, hyperthermophilic extermophiles

  3. Nanoarchaeota: 1 spieces that is obligate symbiont with other speices of archea: found in hydrothermal vents in yellowstone NP & deep-sea vents

  4. Korarchaeota: primitive; found in only one hot spring in yellowstone NP

Roles of Prokaryotes in Ecosystem

  • Present and abundant in every ecosystem in the world

  • Carbon cycle

    • Producers: Photosynthetic bacteria

    • Consumers: use organic compounds from producers and release CO2 to the atmosphere

    • Decomposers: make organic molecules from dead organisms available

  • Nitrogen cycle (completely dependent on bacteria)

    • Nitrogen in the atmosphere (N2) is not usable by plants

    • Nitrogen fixation: N2 is NH3 (ammonia)

    • Ammonification: released during decomposition

    • Nitrification: ammonia converted to nitrate

  • (Plants can’t use nitrogen directly from the air, bacteria pull it from the air and put it into the soil as nitrate for plants to use)

Human Bacterial Diseases

  • In the early 20th century, infectious diseases killed 20% of children before the age of five

  • Sanitation and antibiotics higher survival rates

  • In recent years, however, many bacterial have disappeared and reappeared

Examples of Human Impact by Bacterial Diseases

Dental caries (tooth decay)

  • Plaque consists of bacterial biofilms

  • Streptococcus subrings ferments sugar to lactic acid

  • Tooth enamel degenerates

Peptic ulcer

  • Helicobacter pylori is the main cause

  • Treated with antibiotics

Tuberculosis

  • Mycobacterium tuberculosis

  • The problem for thousands of years

  • Afflicts the respiratory system

  • Easily transferred from person to person through the air

  • Multidrug-resistant (MDR) strains are becoming more common

Black Death

  • The great plague of London killed an estimated 200,000 people or about 20% of the city’s population.

  • The causative agent, the bacterium Yersinia pestis, is a gram-negative, rod-shaped bacterium from the class gamma proteobacteria

  • The disease is transmitted through the bite of an infected flea

Pathways of Infection

  • Natural reservoir: the population of organisms that harbor a pathogen and transmits it to the target population.

    • Reservoir species typically do not experience symptoms of the diseases

    • Bats, rats, cows, etc.

  • Vector species: an organism that transmits a pathogen to another organism

    • Mosquitos, ticks, fleas, etc.

  • Eradication of diseases

    • Smallpox (1980): Vaccination and no natural reservoir

    • Rinderpest (2010): vaccination

Antibiotics and Superbugs

  • Antibiotics: Chemicals produced by microbes or synthetically that prevent the growth of other organisms

    • Ex: penicillin is produced by fungi to stop the growth of bacteria

  • Antibiotic resistance is caused by overuse and misuse of antibiotics

    • Livestock: 70% of antibiotics produced are fed to animals

    • Viral infection

MRSA

  • Methicillin-resistant Staphylococcus aureus

  • Resist to many antibiotics

  • Common in healthcare facilities

    • Mean Age = 68

  • Tight population

    • Mean Age = 23

  • Is not always pathogenic, but can cause diseases such as food poisoning and skin and respiratory infection

Beneficial Prokaryotes

  • Only a small percentage are pathogenic

  • Bacteria are vital to the environment

  • Decomposers release a dead organism’s atoms into the environment

  • Food production: Bread, wine, cheese

Fixation

  • Photosynthesis fixes carbon into sugar

    • Ancient cyanobacteria added oxygen to the air

  • Biology nitrogen fixation

    • Cyanobacteria in aquatic environments

    • Symbiotic nitrogen fixation: sustainable agriculture

Microbial bioremediation

  • Cleaning up oil after the Valdez spill in Alaska, workers hosed oil from beaches and used a floating boom to corral the oil, which was finally skimmed from the water's surface. Some species of bacteria can solubilize and degrade the oil.

  • One of the most catastrophic consequences of oil spills is the damage of fauna

Human Microbiome

  • Food digestion

  • Protection from pathogens

  • produce vitamins

  • Gut microbes can influence our mood, energy level, weight control

  • Allergies & autoimmune diseases

  • Example: Clostridium difficile

    • Part of normal gut biome

    • Suppressed by other microbes

    • Antibiotics disrupt normal levels

    • C. Diff become infectious

Your microbial fauna

  • Equal number of human and bacterial cells in your body

  • Mouth: 100-200 species

  • Skin: up to 1000 species

  • Gut: Up to 1000 species

  • Lungs: 128 species