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 ProkaryotesDOMAIN 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 StructureCell 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 ProkaryotesDOMAIN 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

ArchaebacteriaMethanogens

•Convert H2 & CO2 into methane CH4

•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

c. Spirilla - spiral shaped Ex: Treptonema pallidum

How do bacteria obtain and use energy?

BACTERIA ARE EITHER BACTERIA ARE EITHER

AUTOTROPHIC OR HETEROTROPHICAUTOTROPHIC 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 EnergyObligate 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 O2! EX: Clostridium botulinum, found in soil and can grown in canned food causing fatal food poisoning.

Facultative anaerobes – can survive with or without O2. EX: E. coli, can live in the large intestines contaminated water.

Growth & ReproductionBinary FissionBinary Fission – bacterium doubles in size, it replicates its DNA and divides in half. ASEXUAL

Growth & ReproductionConjugationConjugation – the process by which two living bacteria bind together and one bacterium transfers genetic information to the other.

Sex pili

Conjugation

• http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter13/animation_quiz_3.html

Growth & ReproductionEndosporeEndospore – 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 N2 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 BacteriaPhylum 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 & DiseasePathogen – 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

Evolutionary Arms Race

• http://vitals.nbcnews.com/_news/2013/03/05/17195353-more-bad-news-about-nightmare-bacteria-cdc-says?lite

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.

AntibioticsBacteria 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 & DiseaseEndotoxins – 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 & DiseaseLyme 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 & DiseaseYersinia pestis – the bacterium that causes bubonic plague throughout Europe.

Infected rodents fleas humans.

Bacteria & DiseaseBacillus anthracis

Bacteria & Disease