BACTERIA

Structure of a Bacterium Peptidoglycan Cell wall Cell membrane Ribosome PiliDNA Flagellum

Structure of a Bacterium Capsule: some have a sticky gelatinous capsule around the cell wall (these bacteria are more likely to cause disease) Cell wall: gives the cell shape; composed of a peptidoglycan (sugar- protein complex) Plasma membrane: surrounds the cell and regulates what enters and leaves

Structure of a Bacterium Pilus: hairlike structures emerging from the cell surface; helps bacteria stick to a surface or exchange DNA between bacterial cells Flagellum: long, whiplike structure that enables movement

Structure of a Bacterium Chromosome: single DNA molecule arranged as a circular chromosome; not enclosed in a nucleus Plasmid: small circular chromosome piece containing a few genes

Classifying Bacteria Bacteria are classified according to: Shape Arrangement Gram stain

Classifying Bacteria Shape Spherical - Cocci Rod - Bacilli Corkscrew - Spirillae

Classifying Bacteria Arrangement Singular Pairs – Diplo Chains – Strepto Clusters – Stapylo

Classifying Bacteria Gram stain Staining method involving two dyes The dye absorbed by the bacteria depends on properties of the cell wall Bacteria are either Gram positive or Gram negative Positive stain bluish-purple Negative stain reddish-pink

Prokaryote Cell Wall Structure peptide side chains cell wall peptidoglycan plasma membrane protein Gram-positive bacteria Gram-negative bacteria peptidoglycan plasma membrane outer membrane outer membrane of lipopolysaccharides cell wall peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides That’s important for your doctor to know! Gram-Positive bacteria

Metabolism Obligate aerobes – must have oxygen to survive Obligate anaerobes – cannot live if oxygen is present Facultative anaerobes- can live either with or without oxygen

Archaebacteria & Bacteria Classification 3 Domain system reflects a greater understanding of evolution & molecular evidence Bacteria: Eubacteria Archae: Archaebacteria Eukaryotes: Protists Plants Fungi Animals Prokaryote Eukaryote

Classification of Bacteria All bacteria are prokaryotes Very simple organisms All are unicellular In general, they are smaller than eukaryotes Circular DNA which is not enclosed in a nucleus Lack membrane-bound organelles

Classification of Bacteria Archaebacteria Eubacteria Heterotrophic eubacteria Autotrophic eubacteria Chemosynthetic eubacteria

Archaebacteria a.k.a. Extremophiles Live in oxygen-free environments Obtain energy from sun or inorganic molecules

Archaebacteria: Thiobacilli Heat- and acid-loving bacteria Live in sulfur springs

Archaebacteria: Thiobacilli Consume sulfur Combine it with oxygen to produce energy Produce sulfur dioxide as by-product

Archaebacteria: Thiobacilli Sulfur dioxide can combine with water to form sulfuric acid

Archaebacteria: Halobacteria Salt-loving bacteria Live in saturated salt water like the Great Salt Lake

Archaebacteria: Halobacteria Produce purple pigments Use purple pigment to carry out photosynthesis the way plants use chlorophyll

Archaebacteria: Alkalophytes Live in aquatic environments with high pH Forms the food basis upon which thousands of large organisms are dependent Lake Nakuru

Archaebacteria: Methane Bacteria Cannot live in the presence of oxygen Live in stomachs of cows and sewage treatment ponds

Archaebacteria: Methane Bacteria Obtain energy from CO 2 and hydrogen gas

Archaebacteria: Deep Subsurface Bacteria Live in rocks beneath Earth’s surface (as deep as 3,000 feet)

Archaebacteria: Deep Subsurface Bacteria Obtain energy from H + produced from reaction between minerals in rock and groundwater seeping in

Classification of Bacteria Archaebacteria Eubacteria Heterotrophic eubacteria Autotrophic eubacteria Chemosynthetic eubacteria

Heterotrophic Eubacteria Obtain food from other living organisms parasites Obtain food from dead organisms or organic waste Recycle nutrients in decomposing organic material

Classification of Bacteria Archaebacteria Eubacteria Heterotrophic eubacteria Autotrophic eubacteria Chemosynthetic eubacteria

Autotrophic Eubacteria Obtain energy from light Perform photosynthesis

Autotrophic Eubacteria Cyanobacteria Most contain blue-green pigment (but some are red or yellow) Form chains: not unicellular

Classification of Bacteria Archaebacteria Eubacteria Heterotrophic eubacteria Autotrophic eubacteria Chemosynthetic eubacteria

Chemosynthetic Eubacteria Obtain energy from breakdown of inorganic substances (S and N compounds) Key for agriculture: Convert atmospheric N to a form plants can use

Reproduction in Bacteria Can reproduce rapidly (every 20 minutes) Luckily, most run out of nutrients and water before the colony gets very large Most reproduce by binary fission Bacterium copies its chromosome Old chromosome and copy attach to the plasma membrane at opposite ends Cell grows and becomes larger

Reproduction in Bacteria Most reproduce by binary fission Growth causes two chromosomes to separate Partition forms and separates the cell into two Each new cell has one copy of the original chromosome Creates two cells genetically identical to one another

Genetic Exchange in Bacteria Conjugation Sexual form of bacterial reproduction One bacterium passes all or part of its chromosome to another cell Transfer occurs across pili Creates two bacteria genetically different from one another They then reproduce by binary fission

Transduction: Transfer of genes from one bacterium to another by a bacteriophage. Ex. Toxin gene in Corynebacterium diphtheriae Genetic Exchange in Bacteria

Transformation: Taking in DNA from the outside environment. Ex. Rough Streptococcus pneumoniae transformed into smooth S. pneumoniae. Bacterial species in biofilm communities. Genetic Exchange in Bacteria

Survival If conditions become less than ideal some bacteria can form endospores Tough outer covering resistant to: Drying out Temperature extremes (boiling water) Harsh chemicals

Survival Closturidium botulinum Produces a deadly toxin Endospores can withstand boiling temperatures Canned foods must be pressure cooked to kill the endospores

Six week old infant with botulism, which is evident as a marked loss of muscle tone, especially in the region of the head and neck.

Survival Closturidium tetani Obligate anaerobe that produces a deadly neurotoxin Endospores are found on nearly every surface on the planet When endospores get into a moist, oxygen-free environment (such as inside a puncture wound) they germinate Reason for getting a tetanus shot

Tetanus

Survival Bacillus anthracis Aka. Anthrax Endospores live in soil When inhaled they germinate

Importance to Humans 1. Decomposers 2. Nitrogen-fixers 3. Biotechnology 4. Digestion

Decomposers Break down dead organisms and recycle the nutrients that make them Without decomposition we would run out of the molecules necessary for life

Nitrogen-fixation Plants and animals need nitrogen to make protein The atmosphere is mostly nitrogen but plants and animals can’t use it

Nitrogen-fixation Nitrogen-fixing bacteria convert nitrogen in the atmosphere into nitrogen plants can take up with their roots Animals get their nitrogen by eating plants

Biotechnology Production of foods like butter, cheese, and yogurt Cleaning up oil spills Synthesizing drugs and chemicals

Digestion Much of what we eat would pass through our bodies without being digested if we didn’t have bacteria in our digestive tracts They break down plant matter and synthesize vitamins for us

Bacterial Diseases Bacteria cause illness one of two ways: Breaking down host cells or tissues for food Normal metabolic processes generate toxins

Bacterial Diseases Most food-borne illnesses are caused by bacteria: E. coli comes from infected, undercooked beef Salmonella comes from infected, undercooked poultry (meat and eggs) Botulinum causes botulism – a deadly form of food poisoning

Controlling Bacteria Antibiotics are drugs that kill bacteria (NOT VIRUSES)

Controlling Bacteria Most bacteria like warm, moist, dark conditions Exposing them to other conditions kills them or slows reproduction

Controlling Bacteria Examples: Cooking foods makes it too hot for most bacteria to survive Refrigerating or freezing foods makes it too cold for them to reproduce Drying foods makes it impossible for bacteria to reproduce Pickling causes bacterial cells to burst