Prokayotes Flashcards
Prokaryotes
First inhabitants on earth, They are everywhere
appeared 3.5 - 3.8 billion years ago
Inhibits moderate and extreme environment’s
Microbial Mats
may be the earliest forms of life on Earth
multi-layered sheet of prokaryotes
that includes mostly bacteria, but also archaea
-first microbial mats were at hydrothermal vents.
Stromatolites
Forned by the trapping, binding, and precipitation of minerals by microbial mats of prokaryotes, primarily cyanobacteria.
Earth’s Early Atmosphere
First two billion: Atmosphere was anoxic (no molecular oxygen).
Anaerobic & Autotrophic existed
Autotrophic organisms convert solar energy into chemical energy are phototrophs
Only anaerobic organisms (organism) that can grow without O2) were able to live.
Cyanobacteria
-blue-green algae, evolved from simple phototrophs
- began the oxygenation of the atmosphere
- some O2 is converted into O3 (ozone) and ozone absorbs the ultraviolet light that could cause lethal mutations in DNA.
Extremophiles
Some bacteria and archaea are adapted to grow under extreme conditions
Radioresistant organisms have adapted to survive high levels of radiation. ( Deinococus radiorans)
Preferred Conditions of Extremophiles
- Acidophiles: pH 3 or below
- Alkaliphiles: 9 or above
- Thermophiles: Temperature 60–80 °C (140–176 °F)
- Hyperthermophiles: Temperature 80–122 °C (176–250 °F)
- Psychrophiles: Temperature of −15–10 °C (5–50 °F) or lower
- Halophiles: Salt concentration of at least 0.2M
- Osmophiles: High sugar concentration
Culturing Prokaryotes
Microbiologists growing prokaryotes in the laboratory using a culture medium containing all the nutrients needed by the target organism.
Medium: can be liquid, broth, or solid.
After incubation time at the right temperature, evidence of microbial growth appears
Can all prokaryotes be grown in a lab?
NO over 99 percent of bacteria and archaea are unculturable due to lack of knowledge
Culturable organisms can become unculturable under stressful conditions
Biofilms
microbial community held together in a gummy-textured matrix that consists of polysaccharides secreted by the organisms, together with some proteins and nucleic acids
Biofilms grow attached to surfaces
Living in a biofilm makes microbes stronger and more resistant than those floating freely in liquid
Stages of Biofilm Development
1.Initial attachment: Bacteria adhere to a solid surface via weak van der Waals
interactions.
2.Irreversible attachment: They anchor themselves more firmly using tiny hair-like structures called pili.
3.Maturation I: Biofilm grows through cell division and recruitment of other bacteria. An extracellular matrix composed primarily of polysaccharides holds the biofilm together.
4.Maturation II: The biofilm becomes larger and more complex.
5.Dispersal: Parts of the biofilm break down, releasing bacteria to spread and form new biofilms elsewhere.
Prokaryote Shapes
Three categories:
- Cocci, or spherical (a pair is shown)
- Bacilli, or rod-shaped
- Spirilli, or spiral-shaped.
Prokaryote Structure
Circular DNA in the nucleoid
Cell wall
capsule, flagella and pili
Prokaryote Reproduction
Asexual Reproduction usually occurs by binary fission
Chromosome is replicated resulting in copies separate due to growth of the cell, as the cell grows two copies move apart then the cell pinches in the middle & splits into two identical cells
prokaryotes can share genes by three other mechanisms.
Transformation:
Cell takes up prokaryotic DNA directly from the environment, may stay separate as a plasmid or merge with its own DNA.
Transduction: virus injects DNA into the cell that has a small fragment of DNA from a different prokaryote.
Conjugation: DNA is transferred from one cell to another through mating bridge which connects two cells after the sex pilus draws the two bacteria
Bacteria and Archaea
Differ in the lipid composition of their cell membranes and the characteristics of the cell wall.
Archaeal Phospholipid Differences from bacteria
- Branched phytanyl sidechains instead of linear ones.
- Ether bond instead of an ester bond connects the lipid to the glycerol.
Cell Wall Differences
Bacterial cell walls contain peptidoglycan & archaean walls do not, may have pseudopeptidoglycan, polysaccharides, glycoproteins, or protein-based cell walls.
Groups of Bacteria
Gram positive and Gram negative, based on the Gram stain reaction.
Gram-positive: have a thick cell wall, together with teichoic acids.
Gram-negative: have a thin cell wall and an outer envelope containing lipopolysaccharides and lipoproteins.
Similar, differences: Bacteria & Archaea
Similar
Prokaryotic, cell morphology variable, as a lipid bilayer cell membrane
Differences:
Bacteria has peptidoglycan & Archaea do not
Archaea has a lipid monolayer as a cell membrane type & bacteria do not
Bacteria has fatty acids plasma membrane lipids & archaea has phytanyl groups
Metabolism in Prokaryotes
For cells to build molecules to sustain life they need nutrients
Nutrients in large amounts -> Macronutrient’s (Carbon, hydrogen, oxygen, nitrogen, phosphorus & sulfur)
Nutrients smaller - Micronutrients
How Prokaryotes get Energy
The Carbon Cycle & The Nitrogen Cycle
Prokaryotic Organisms Cause Numerous Diseases
Epidemic - Individuals in a population at the same time
Pandemic - worldwide
Endemic - constantly present at low incidence
Foodborne Illnesses
illness resulting from the consumption the pathogenic bacteria, viruses, or other parasites that contaminate food
In the past, it was relatively common to hear about sporadic cases of botulism.
Most modern cases are now linked to produce.
Biofilms and Diseases
Resistant to attempts to destroy them
Biofilm infections develop gradually; sometimes, they do not cause symptoms immediately.
Rarely resolved by host defense mechanisms & Biofilm is very difficult to get rid off
Superbugs
An antibiotic is a chemical, produced either by microbes or synthetically, that is hostile to the growth of other organisms
causes of resistant bacteria is the abuse of antibiotics. The imprudent and excessive use of antibiotic
