Bacteria

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

Bacteria Characteristics Unicellular Circular DNA No organelles except ribosomes 1/10 th - 1/1000 th the size of eukaryotic cells Flagella-long hair-like structure used for movement Reproduce asexually –Binary Fission

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 (energy from light) some use chemosynthesis (energy from inorganic chemicals) Heterotroph – “other feeding” many bacteria are unable to produce their own food and are required to absorb energy sources from other things

Bacterial Characteristics: Metabolic diversity continued obligate aerobe – like us, these bacteria must have oxygen obligate anaerobe – these bacteria need to be in an oxygen-free environment such as the human gut, or they will die facultative anaerobe – these bacteria can live in either an oxygen or oxygen- free environment

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

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 of lipopolysaccharide - this extra layer inhibits the uptake of antibiotics – protecting the bacteria cell membrane cell wall cell membrane Outer membrane lipopolysaccharide cell wall

Gram+ vs Gram- Absorb stain appear purple Don’t absorb stain appear pink The type of cell wall is used by doctors to help diagnose disease The bacteria are stained with a special stain called Gram stain Bacteria without the extra membrane, appear purple. These are Gram positive (Gram +) bacteria Bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria

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

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

Exchanging Genetic Information

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

Transformation: Bacteria absorb “naked” DNA from their environment

Conjugation

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

Bacteria Play Important Roles in Ecosystems Decomposers recycle dead organisms releasing their nutrients back to the environment for use by other organisms – (C,H,O,N,P,S) 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 How do living things use nitrogen? (Hint: Check your protein notes)

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 (H 2 S) 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 We have 10X more bacterial cells than human cells. Yes, that’s right – 10X more bacterial cells than human cells! Go tell Mrs. Glodowski what you think about that!

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 can - - 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. (Think 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 used to fight disease - discovered accidently by Alexander Fleming in 1928 The discovery of antibiotics revolutionized the treatment of disease

Antibiotic Action Antibiotics affect bacteria, but not eukaryotic cells Antibiotics attack bacteria in 5 ways some damage 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

Antibiotic Resistance Some bacteria have developed resistance to the effect of some antibiotics, and the number is growing. The problem is increased by overuse and misuse of antibiotics *use of antibiotics to treat viral infections – antibiotics don’t affect viruses *use of antibiotics in livestock (cattle, chickens, pigs) - antibiotics show up in the meat and milk at subtherapeutic levels *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, and they have less competition for resources

Black Plague-Yersinia pestis

Syphilis--Treponema pallidum/Bacterial

Mycobacterium leprae/Bacteria

Clostridium perfringes/Bacteria

Vocabulary autotroph pili heterotroph nucleoid peptidoglycan capsule plasmid conjugation bridge Gram -obligate aerobe Gram +obligate anaerobe binary fissionfacultative anaerobe conjugationnitrogen fixing bacteria transductioncyanobacteria transformationpathogens biofilm