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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 1/10th - 1/1000th 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 oxygenfree environment Bacterial Structure Cell Wall Cell Membrane Pilus chromosome nucleoid capsule plasmid cytoplasm flagellum ribosome 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 wall cell membrane cell membrane lipopolysaccharide cell wall Outer membrane Gram+ vs GramThe 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 Absorb stain appear purple Bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria Don’t absorb stain appear pink 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 Plasmid Conjugation 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 (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 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 some some some some damage cell walls or prevent new cell wall from forming damage the cell membrane prevent protein synthesis prevent DNA from being copied 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 heterotroph peptidoglycan plasmid Gram Gram + binary fission conjugation transduction transformation biofilm pili nucleoid capsule conjugation bridge obligate aerobe obligate anaerobe facultative anaerobe nitrogen fixing bacteria cyanobacteria pathogens
