Prokaryotes Or 100 Trillion Friends That You Didn’t Know You Had

The Human Microbiome We are actually a giant ecosystem of microbes Prokaryotes comprise between 1-3% of the mass of a human body - up to 6lbs of a 200 lb person can be microbes

Classification: Some Old, Some New Biologists have typically classified living things into 5 large groups called kingdoms - Monera, Protista, Fungi, Plantae & Animalia Then biologists discovered organisms called Archea – they are prokaryotic organisms but aren’t bacteria. - What to do?

The Challenge of Archea Archea present a problem, they a are prokaryotes – They have no nucleus or organelles They also share traits with eukaryotes - similarities in DNA and synthesis They have traits unique to themselves - cell membrane lipids, ability to survive extremely high temperature

Enter the Domain System of Classification Scientists divided living things into 3 Supergroups called domains these consist of Bacteria, Archea and Eukarya

Archea can be Extremophiles Some species of archea can be found in environments so extreme, that nothing else lives there- extreme temps, extreme pH, extremely salty etc…

Bacteria Earth’s oldest life forms – between 3.5 and 3.8 billion years old Most abundant life form – up to 2.5 billion individual bacteria in 1 gram of fertile soil Very adaptable – found in all of Earth’s ecosystems 7

Bacteria Characteristics Unicellular Circular DNA No organelles 1/10th the size of eukaryotic cells Flagella-long hair-like structure used for movement Reproduce asexually –Binary Fission 8

Bacterial Shapes 3 main shapes - coccus – sphere - bacillus – rods - spirillum - spiral

Bacterial Characteristics Metabolic diversity – Bacteria can produce energy in a variety of circumstances autotroph – (self-feeding) – some bacteria can produce their own food - some use photosynthesis – get energy from light - some use chemosynthesis – get energy from chemicals Heterotroph - (other feeding) – many bacteria are unable to produce their own food and are required to eat other things 10

Bacterial Characteristics: Metabolic diversity continued obligate aerobe – like us these bacteria need oxygen obligate anaerobe - these bacteria need to be in an oxygen free environment – human gut facultative anaerobe – these bacteria can live in either an oxygen or oxygen free environment

Bacterial Structure Cell Wall Cell Membrane Pilus chromosome nucleoid capsule ribosome plasmid cytoplasm flagellum

Bacterial Structure: Cell Wall Made of peptidoglycan – a combination of protein and polysaccharides Some bacteria called Gram negative bacteria have an additional layer of membrane that contains lipopolysaccharide - this extra layer inhibits the uptake of antibiotics – protecting the bacteria cell wall cell membrane cell membrane lipopolysaccharide cell wall Outer membrane

Gram + vs. Gram - The type of cell wall is used by doctors to help diagnose disease The bacteria are stained with a special stain called Gram stain Absorb stain appear purple Bacteria without the extra membrane, appear purple. These are Gram positive (Gram +) bacteria Named after Danish Scientist Hans Christian Gram – No Joke Gram was working on Pneumonia and discovered that different organisms took up stain differently. The process stains the both types of cells with crystal violet, and then they are treated with alcohol which Bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria Don’t absorb stain appear pink 14

Bacterial Structure continued Pili – hairlike structures usually found in Gram neg. bacteria. Help the bacteria stick to surfaces. Also forms conjugation bridge Chromosome – a single loop of DNA that is folded on itself - controls the cell’s function Nucleoid – the region of the cytoplasm where the DNA is found Plasmid – an accessory loop of DNA – small contains only a few genes - can be responsible for: conjugation, antibiotic resistance, unique metabolic properties – like the ability to use hydrocarbons Capsule – found outside some bacteria stores nutrients and protects the bacteria from changing environmental conditions

Reproduction - Binary Fission Bacterial cells undergoing binary fission 16

Reproduction - Binary Fission Asexual reproduction - offspring are genetically identical to parent – no new genetic combinations - under ideal conditions can occur every 20 min - creates large numbers of bacteria in a short time

Each spot represents a single bacterial cell that reproduced by binary fission to produce millions of genetically identical cells. Genetically identical, good or bad?

Exchanging Genetic Information Bacterial cells need to be able to exchange genetic information - creates new genetic combinations which increases the ability of the bacteria to survive Bacteria have 3 methods for exchanging DNA -Transduction – viruses carry DNA from one bacterial cell to another -Transformation – bacteria can absorb “naked” DNA released by dead bacteria from the environment - Conjugation – two bacteria join at a conjugation bridge, one bacteria passes on a copy of its plasmid or chromosome 19

Exchanging Genetic Information

Transduction – DNA is carried from one bacteria to another by a virus 21

Transformation: Bacteria absorb “naked” DNA from the environment 22

Conjugation 23

Conjugation- one cell passes a copy of its plasmid or chromosome to another Recipient Cell Donor Cell A special pilus forms a connection called a conjugation bridge between 2 bacterial cells Plasmid Conjugation bridge The donor cell copies its plasmid or chromosome and passes the copy through the conjugation bridge Cells separate 24

Bacteria Play Important Roles in Ecosystems Decomposers – recycle dead organisms releasing their nutrients back to the environment for use by other organisms – SPONCH Without decomposers, the elements on earth would have remained locked up in dead organisms and life would have ceased

Bacterial Roles: Nitrogen Fixation some bacteria contain enzymes which allow them to convert (or fix) nitrogen from the air into a useable form - they are nitrogen fixing bacteria - Why do living things use nitrogen?

Bacterial Roles: Producers In some ecosystems chemosynthetic and photosynthetic bacteria serve as the basis of the food chain – chemosynthetic bacteria in deep ocean vents convert hydrogen sulfide (H2S) gas into energy - cyanobacteria are photosynthetic bacteria which act as producers in many aquatic ecosystems

Bacterial Roles: Symbiotic Bacteria Many bacteria live in or on other organisms (including humans) and aid their host - some live in the gut of herbivores helping to digest cellulose - bacteria in the gut of humans aid digestion and produce vitamins - bacteria on skin and in body openings help prevent infection by harmful organisms Stomach bacteria help maintain stomach pH, produce B and K vitamins, studies show that babies given lactobacilius bacteria have less diarrhea

Bacterial Roles: Pathogenic Bacteria Pathogens are organisms that cause disease - only a small portion of bacteria are pathogens - most bacteria diseases are caused by toxins released by the bacteria - these toxins: - poison cells and damage tissue - interfere with cell signaling - over-stimulate cells causing them to malfunction

Pathogenic Bacteria: Biofilms Some bacteria can form a biofilm – a matrix made of polysaccharide - once formed, the matrix traps other bacteria - the biofilm protects the bacteria, making it hard to kill them Biofilms form on joint replacements, contact lenses, plaque on your teeth.

Antibiotics Antibiotics are chemicals which either kill bacteria or prevent their growth and reproduction Bacteria and other microbes produce antibiotics to reduce competition from other organisms Penicillin was the first to be use to fight disease - discovered accidently by Alexander Fleming in 1928 Two scientists Walter Florey and Ernst Chain determined how to use penicillin to treat disease in 1939. The discovery of antibiotics revolutionized the treatment of disease Antibiotics which kill bacteria are bacteriacidal, the antibiotics which stop growth are referred to as bacteriastatic

Antibiotic Action Antibiotics effect bacteria, but not eukaryotic cells Antibiotics attack bacteria in 5 ways - some damage the cell walls or prevent new cell wall from forming - some damage the cell membrane - some prevent protein synthesis - some prevent DNA from being copied - some interfere with bacterial metabolism Bacterial ribosomes are 70S 50S and 30S subunits – antibiotics impact these subunits Eukaryotic ribosomes are 80S 60S and 40S subunits – antibiotics don’t impact these

Antibiotic Resistance Some bacteria have developed a resistance to the effect of some antibiotics - the number of resistant bacteria is growing The problem is increased by overuse and misuse of antibiotics - use of antibiotics to treat viral infections – antibiotics don’t effect viruses - the use of antibiotics in livestock (cattle, chickens, pigs) antibiotics show up in the meat and milk - people take the antibiotics until they feel better, but stop before all of the bacteria are destroyed - this kills the most susceptible bacteria, but leaves the more resistant bacteria

Black Plague-Yersinia pestis Bacillus bacterium from flea bites that recently fed on infected rats. Flea regurgitates germs onto human open wound. Sign of infection is lymph nodes swellings called Buboes. Dried blood under the skin turns black, hence the name Black Death. Spread is slow from person to person. Mortality is very high (75%) for untreated cases. Now early treatment with antibiotics is very effective. 34

Syphilis--Treponema pallidum/Bacterial Causes an ulcer at the site of infection. 4 stages of life. Treatment now with Penicillin. 35

Mycobacterium leprae/Bacteria Rod like Bacteria-spread through coughing and sneezing. In old days they thought it was genetic and they isolated people-Leprae colonies. Now (1940)there is antibiotic treatment to clear up the symptoms in 6-12 months. 36

Clostridium perfringes/Bacteria Gram positive bacillus. Can cause gas gangrene. Often caused from fecal contamination of a wound Usually in the buttocks, thighs, and perineum. Infection may proceed up to 10cm per hour. Often produces large amounts of CO2 and hydrogen . 37

Vocabulary Microbiome Archea autotroph pili heterotroph nucleoid peptidoglycan capsule plasmid conjugation bridge Gram - obligate aerobe Gram + obligate anaerobe binary fission facultative anaerobe conjugation nitrogen fixing bacteria transduction cyanobacteria transformation pathogens biofilm 38