Prokaryotes Life Science

What are Prokaryotes?  Single-celled organisms  Very tiny  Cannot be seen without a microscope  Our microscopes are not powerful enough  Lack a nucleus and most other organelles  Most numerous organisms on Earth  Extremely important organisms.

Classification and Evolution  Prokaryotes are split into 2 Domains (Recall Taxonomic Levels?)  Domain Bacteria  Domain Archaea  Everything else on Earth is in Domain Eukarya  Prokaryotes were the first living things to evolve, around 3.8 billion years ago  Only living things on earth until 2 billion years ago  Until 1970s, Archaea were considered to be bacteria (called Archaebacteria)  As more was learned about them, they were given their own domain because they are VERY different from bacteria  Your textbook still has them listed as bacteria…

Domain Bacteria  Made up of bacteria (surprised?)  Only 1 kingdom-Can you guess what it’s called?  Most abundant living things on Earth.  Live in almost every environment  Air  Ocean  Soil  Intestines  Estimated number of bacteria on earth: 5,000,000,000,000,000,000,000,000,000,000  You have 10 times more bacterial cells than human cells!

Classification of Bacteria  Thousands of bacterial species exist.  Many are classified by shape.  Others are classified based on the color that they stain (Gram staining)

Bacterial shapes  Baccili:  Rod shaped  Cocci:  Sphere-shaped  Spirilli  Spiral-shaped

Structure of Bacterial Cells  Bacterial cells are surrounded by a plasma membrane  Most also have cell walls  Surrounding the membranes and cell wall (if present) is a capsule, which further protects the cells  Inside of the bacterial cell is cytoplasm, similar to eukaryotic cells  Floating in the cytoplasm are ribosomes and plasmids (small sections of DNA)  There is no nucleus  Instead, there is a Nucleoid (circular DNA)  Bacterial cells also may contain whip-like structures called flagella

Structure of Bacterial Cells

How do bacteria get energy?  Some are photosynthetic  Others decompose organic matter  Some can use chemicals from the environment to do a process similar to photosynthesis (called chemosynthesis)  Example: Nitrogen fixation  Mutualism  Getting resources from other species, while providing some service to that species (+/+)  Parasitism  Stealing resources from host organisms (+/-)

Bacteria and People  You may think that bacteria’s purpose is to make us sick  For some bacteria, this is true  For many others, it is not  Benefits of Bacteria  Create medicine, such as vaccines  Help us digest foods and produce vitamins  Decompose wastes  Fix Nitrogen into usable forms for plants  Make foods such as cottage cheese, yogurt, cheese, and many more.

Dark side of Bacteria  Some bacteria can lead to disease  Clostridium tetani  Tetanus aka Lockjaw  Affects muscles (including the heart). Leads to muscle spasms, and can be fatal.  Escherichia coli  E. Coli  Many strains exist in human intestines in a commensalism relationship. However, some can cause food poisoning.  Transmitted by fecal-oral route. WASH YOUR HANDS AFTER USING THE BATHROOM!!!  Salmonella bongori & Salmonella enterica  Salmonella  Cause Typhoid fever (very fatal) and Food Poisoning  Transmitted by fecal-oral route. WASH YOUR HANDS AFTER USING THE BATHROOM!!!

Dark side of Bacteria Continued  Staphylococcus (many species)  Sinus infections, ear infections, skin infections, food poisoning  Streptococcus (Many species)  Pneumonia, necrotizing fasciitis (flesh-eating bacteria), pink eye  Mycobacterium tuberculosis  Tuberculosis  Second deadliest infectious disease (After HIV/AIDS).  Yersinia pestis  “The Bubonic Plague” or “The Black Death  Killed over 1/3 of the European Population between 1347 and 1353

Controlling Bacteria  Bacteria in food and water can be killed by cooking at a high temperature  Bacteria on surfaces can be killed with cleaning products such as bleach or Lysol  Antibiotics can be used to kill bacteria that are harming humans  Effective against bacterial infections such as strep throat, sinus infections, ear infections, pneumonia, etc.  However, there is a problem

Antibiotic Resistance in Bacteria  Some bacterial species are evolving resistance to antibiotics.  The antibiotic kills those that are not resistant, but leaves the one that are resistant  Example: Clostridium difficile is a common bacteria that causes diarrheal disease in hospitals. Hospitals, due to their obsessive cleaning procedures, have selected for resistant strains. Patients are being infected at a high rate, while staying in hospitals.

Even more alarming…  Remember how we just learned that Tuberculosis is the 2 nd most deadly infectious disease… Well…  Tuberculosis is spreading due to becoming resistant to the antibiotics typically used to treat it.  One strain is totally resistant to ALL drugs currently used  Another is resistant to 3 of the 6 drugs used to treat it.

Domain Archaea  Only 1 Kingdom  Called Archaea (Surprised?)  Prokaryotes  First discovered in extreme environments  Originally classified as bacteria  As more was learned about them, they were found to be VERY different from bacteria  They were given their own Domain and Kingdom  Very little is known about these organisms

Archaea: Tiny but Tough  Many archaea are extremophiles  Organisms that have evolved to live in extreme conditions.  Example: Hydrothermal vents in the ocean (picture) are very acidic and hot.  Would kill most organisms, yet archaea thrive.  4 types of extremophiles  Halophiles-Survive in very salty water (Dead sea)  Hyperthermophiles- Survive at high heats  Some archaea can survive up to 122° C (252° F)  Acidophiles-Live in highly acidic environments (like near volcanoes)  Alkaliphiles-Live in very basic environments

Where else do they live?  Ar chaea do not only live in extreme environments  They are found nearly everywhere on Earth.  Including in humans (many are found in the human belly button!)  Around 4 % of human microbiome  They are also important decomposers, and part of Nitrogen cycle  Many archaea also form symbiotic relationships  None are known parasites  Most form mutualistic relationships  Archaea in cattle gut help break down grass and straw, and get nutrients in return