Presentation on theme: "Objectives To understand the structure of bacteria –Compared to viruses Understand Eubacteria vs. Archaebacteria How bacteria classified –Kingdom, phyla,"— Presentation transcript:
Objectives To understand the structure of bacteria –Compared to viruses Understand Eubacteria vs. Archaebacteria How bacteria classified –Kingdom, phyla, etc. How bacteria reproduce Uses and harmful effects of bacteria How to prevent bacteria –Compared to viruses
Chapter 19: Bacteria
How Human are you? There are more microbial cells in our bodies than there are human cells! Of the 100 trillion cells that make-up the human body 90 trillion are bacterial Humans are ~90% Bacterial Everyone has about 1 kg in weight of bacteria in their gut. Each gram of feces contains 100,000,000,000 (100 billion) microbes. Human adults excrete their own weight in fecal bacteria every year.
Bacteria: Structure CELLS (living) Prokaryotic (No nucleus or MBO’s) Genetic Material (DNA) Cell Membranes and Cell Walls
Classifying Prokaryotes DOMAIN BACTERIA – Kingdom Eubacteria Single-celled prokaryote Have peptidoglycan cell walls (protein carbohydrate) Can form colonies of clumps or filaments. Three basic shapes: Cocci (round), bacilli (rod) & spirilla (spiral) Strepto – occurs in chains. Staphylo – occurs in clusters..
Basic Structure Cell wall – protects the cell & gives it shape. Outer membrane – protects the cell against some antibiotics (only present in gram-negative) Cell membrane – regulates movement of materials into & out of the cell; contains enzymes important to cellular respiration. Ribosome Cell Membrane Cell Wall Pilli Flagella DNA (circular = plasmid) Peptidoglycan
Plasmid – circular piece of DNA that contains some genes obtained through genetic recombination. Capsule & Slime layer – protect the cell & assist in attaching the cell to other surfaces. DNA (circular = plasmid)
Classifying Prokaryotes DOMAIN ARCHAEA – Kingdom Archaebacteria Genes that resemble eukaryotic genes & some that resemble prokaryotes. Have unusual lipids in their cell membranes Found in EXTREME environments! Cell walls lack peptidoglycan Have introns in their DNA Single-celled prokaryote
Archaebacteria Methanogens Convert H 2 & CO 2 into methane CH 4 Anaerobic bacteria (no oxygen… early Earth) Found in bottoms of swamps, sewage & intestinal tracts of animals. Extreme Halophiles Salt loving Found in Great Salt Lake & Dead Sea Thermoacidophiles Live in extreme acidic & hot environment
Archaebacteria vs Eubacteria Type of environment: EXTREME Cell Wall composition: LACKS PEPTIDOGLYCAN Type of environment: COMMON Cell Wall composition: PEPTIDOGLYCAN
Prokaryote Evolution Fossil Evidence indicates bacteria existed about 3.5 billion years ago. Eukaryotes existed about 2.5 billion years ago (Theory of symbiosis) Bacteria evolved to adapt to almost any environment, from ocean trenches to thermal vents.
Identifying Prokaryotes Prokaryotes are identified by characteristics such as: the way they obtain energy shape type of cell wall the way they move
V. Ways Bacteria are Identified I. Shapes of Bacteria: a. Bacilli - rod-shaped
b. Cocci - round shaped Staphylococcus - cocci in clusters Streptococcus - cocci in chains Diplococcus - cocci in pairs
How do bacteria obtain and use energy? BACTERIA ARE EITHER AUTOTROPHIC OR HETEROTROPHIC Chemoheterotrophs – organisms that must take in organic molecules for both energy and a supply of carbon. Photoheterotrophs – organisms that are photosynthetic, but still need to take in organic compounds as a carbon source. Chemoautotrophs – make organic carbon molecules from carbon dioxide and other inorganic compounds using energy from chemical reactions. Photoautotrophs – use energy from sunlight to convert carbon dioxide and water to carbon compounds.
Releasing Energy Obligate aerobes – organisms that require a constant supply of oxygen in order to live. EX: Mycobacterium tuberculosis, the bacterium that causes tuberculosis. Obligate anaerobes – do not require oxygen; some may be killed by O 2 ! EX: Clostridium botulinum, found in soil and can grown in canned food causing fatal food poisoning. Facultative anaerobes – can survive with or without O 2. EX: E. coli, can live in the large intestines contaminated water.
Growth & Reproduction Binary Fission Binary Fission – bacterium doubles in size, it replicates its DNA and divides in half. ASEXUAL
Growth & Reproduction Conjugation Conjugation – the process by which two living bacteria bind together and one bacterium transfers genetic information to the other. Sex pili
Growth & Reproduction Endospore Endospore – adaptation that protects the cell against harsh environmental conditions, such as heat and drought. May allow the bacterium to survive for thousands of years.
How do Bacteria benefit humans and ecosystems? 1. Decomposers – recycle nutrients: break down the nutrients in dead matter & atmosphere. 2. Nitrogen – Fixing Bacteria (Nitrogen fixation) Live freely & symbiotically with plants Rhizobium; converts N 2 into a form of nitrogen plants can use. Found in legumes (bean type plants) 3. Aid in digestion – live symbiotically within our GI tracts and help us extract nutrients
Bacteria and the Nitrogen Cycle
Importance of Bacteria Phylum Cyanobacteria Photosynthetic Eutrophication or Population Bloom – the sudden increase in the number of cyanobacteria due to a high availability of nutrients. Leads to anoxic environment (dead zone)
Human Uses of Bacteria Food – baking & beverages Clean up oil spills, rivers & streams Pharmaceuticals Aide in digestion (symbiotic relationship with bacteria in our guts)
Bacteria & Disease Pathogen – any disease-causing agent Only 1% of bacteria are pathogenic! Exotoxins – toxic proteins secreted by bacterial cells, includes some of the most potent poisons known. Clostridium botulinum – one gram of the exotoxin that causes botulism could kill 1,000,000 people!
MRSA Staphylococcus aureus – harmless, found on skin; if it enters the body through a wound it can cause layers of skin to slough off, vomiting, severe diarrhea & deadly toxic shock syndrome. MRSA = methicillin resistant Staphylococcus aureus
Antibiotics: how we TREAT bacterial infections Antibiotics are drugs that combat bacteria by interfering with various cellular functions Some bacteria are antibiotic-resistant and destroy antibiotics, or prevent entry of the antibiotic into the cytoplasm.
Antibiotics Bacteria can be tested for their sensitivity to antibiotics by growing them in a petri dish with paper disks containing different antibiotics. As the antibiotics diffuse into the agar, the bacteria’s growth will be inherited by the antibiotics if the bacteria are sensitive to that antibiotic.
Bacteria & Disease Endotoxins – are NOT secretions; but components of cell walls in bacteria: glycolipids, which are large molecular complexes of polysaccharides & lipids. All endotoxins induce the same general symptoms: fever, aches and sometimes a dangerous drop in blood pressure (shock). Salmonella – produces endotoxins that cause food poisoning & typhoid fever.
Bacteria & Disease Lyme Disease Most widespread pest carried disease in U.S. Caused by Borrelia burgdorferi, a bacterium carried by ticks that live on deer & field mice. Antibiotics can cure the disease if administered within a month of exposure. If untreated, it can lead to arthritis, heart disease & nervous disorders.
Bacteria & Disease Yersinia pestis – the bacterium that causes bubonic plague throughout Europe. Infected rodents fleas humans.