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Chapter 27: Bacteria and Archaea Outline

I. Categories of life

A. Domains

B. Eukaryote vs Prokaryote

II. Domain Bacteria

A. cell walls, structure

B. Bacterial reproduction

C. Nitrogen fixation

D. Pathogenic bacteria

III. Domain Archaea

Why care about the small stuff

Bacteria are important “nitrogen fixers”

Bacteria and fungi are decomposers

Some bacteria and algae can produce

oxygen

They are everywhere!!

Some can produce disease

Good website:

http://www.bacteriamuseum.org/cms/

Prokaryotes

Prokaryotes thrive almost everywhere, including

places too acidic, salty, cold, or hot for most

other organisms

Most prokaryotes are microscopic, but what

they lack in size they make up for in numbers

There are more in a handful of fertile soil than

the number of people who have ever lived

Prokaryotes are divided into two domains:

bacteria and archaea

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Bacteria in our bodies

Bacteria are found naturally in our bodies

including in our:

Nasal cavity (nose)

Large intestine

On our skin

Staphylococcus

in the human

nasal passage

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Euprymna Scolopes have a symbiotic

relationship with luminescent bacteria.

Photo courtesy of Margaret McFall-Ngai.

Do prokaryotes have a nucleus

1. Yes

2. No

Yes N

o

50%50%

Are Domain Bacteria and Domain Archaea

prokaryotic or eukaryotic?

1. prokaryotic

2. eukaryotic

pro

kary

otic

euka

ryotic

50%50%

The First Cells

Microfossils are fossilized forms of microscopic

life

-Oldest are 3.5 billion years old

The First Cells

Stromatolites are mats of cyanobacterial cells

that trap mineral deposits

-Oldest are 2.7 billion years old

Prokaryotes

Domain Archaea – live in extreme

environments

Domain Bacteria (Eubacteria)

Microorganisms are any small organism – too

small to see with the naked eye include

Pathogens – cause disease

Most bacteria are not pathogens

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Prokaryotic Characteristics

1. Unicellular

2. No membrane-bound nucleus, single

chromosome and histone-like proteins found

in nucleoid region

3. Lack membrane bound organelles

4. Contain ribosomes

Prokaryotic Characteristics

5. Many have flagella

6. Cell wall present in many species

7. Have plasma membrane

8. Reproduction by prokaryotic fission

9. Great metabolic diversity

Prokaryotes

No membrane bound organelles including:

nucleus, mitochondria, chloroplasts,

endoplasmic reticulum, golgi complex,

lysosomes.

They do contain small ribosomes, storage

granules, plasma membrane may be folded

Domain Bacteria

Prokarotes

Categorized by

1. Shape

2. Cell wall type

3. Where they get their energy and their

nutrients from.

4. Motility

Based on these molecular data, several

prokaryotic groupings have been proposed

Bergey’s Manual of Systematic Bacteriology

Contains about 7,000 bacterial and archaeal

species

The three-domain (Woese) system of phylogeny

is based on rRNA sequences

Molecular Classification

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Molecular Classification Categories by shape

Cocci – spherical (round ball) shaped, may

be singly or in groups

Bacilli – rod shaped, may occur as a single

rod or as chains of rods

Spirilla – helical, spiral shaped

Most prokaryotes have one of 3 basic shapes

Bacillus = Rod-shaped

Coccus = Spherical

Spirillum = Helical-shaped

Prokaryotic Shapes Figure 27.2

(a) Spherical (b) Rod-shaped (c) Spiral

1

m

1

m

3

m

Diverse nutritional and metabolic

adaptations have evolved in prokaryotes

Prokaryotes can be categorized by how they obtain

energy and carbon

Phototrophs obtain energy from light

Chemotrophs obtain energy from chemicals

Autotrophs require CO2 as a carbon source

Heterotrophs require an organic nutrient to make

organic compounds

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Energy and carbon sources are combined to give

four major modes of nutrition:

Photoautotrophy

Chemoautotrophy

Photoheterotrophy

Chemoheterotrophy

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Diverse nutritional and metabolic

adaptations have evolved in prokaryotes

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Table 27.1

The Role of Oxygen in Metabolism

Prokaryotic metabolism varies with respect to O2

– Obligate aerobes require O2 for cellular

respiration

– Obligate anaerobes are poisoned by O2 and use

fermentation or anaerobic respiration

– Facultative anaerobes can survive with or without

O2

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Nitrogen Metabolism

Nitrogen is essential for the production of amino

acids and nucleic acids

Prokaryotes can metabolize nitrogen in a variety

of ways

In nitrogen fixation, some prokaryotes convert

atmospheric nitrogen (N2) to ammonia (NH3)

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Nitrogen Fixation

Some bacteria are able to take nitrogen gas and

fix it in the form that can be used by plants

Rhizobium fixes nitrogen for plants like

legumes.

Legumes and Rhizobium live in a mutualistic

relationship

Rhizobium provide usable nitrogen

Legumes provide sugar

Rhizobium live inside legume cells in nodules

Metabolic Cooperation

Cooperation between prokaryotes allows them

to use environmental resources they could not

use as individual cells

In the cyanobacterium Anabaena,

photosynthetic cells and nitrogen-fixing cells

called heterocysts (or heterocytes) exchange

metabolic products

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Figure 27.14

Photosynthetic

cells

Heterocyst

20 m

Eutrophication

Cyanobacteria like Anabaena are nitrogen fixers

(use heterocysts)

Phosphorus and nitrogen are the main limiting

mineral in natural ecosystems

Ph & N sources include sewage, agricultural

runoff (fertilizers), and industry

Ph & N that enters rivers, lakes and estuaries can

produce blooms of cyanobacteria

Eutrophication

This bloom of bacteria covers the top of the

pond, blocking light from reaching the water

plants below.

The water plants are not able to

photosynthesize so they can’t produce oxygen

Cyanobacteria have a short life and die,

decomposers break them down. Decomposers

use oxygen.

Eutrophication

Oxygen is depleted by decomposers, and

blooms block out light which decreases

photosynthesis

End result – oxygen depletion, fish need

oxygen and will die.

Photoautotroph - cyanobacteria

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These organisms use the energy from the sun to fix

carbon into a sugar from CO2

1. Photoheterotrophs

2. Chemoheterotrophs

3. Photoautotrophs

4. Chemoautotrophs

Photo

hete

rotrophs

Chem

ohete

rotrophs

Photo

auto

troph

s

Chem

oauto

troph

s

25% 25%25%25%

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These organisms use the energy from inorganic

compounds to fix carbon into a sugar from CO2

1. Photoheterotrophs

2. Chemoheterotrophs

3. Photoautotrophs

4. Chemoautotrophs

Photo

hete

rotrophs

Chem

ohete

rotrophs

Photo

auto

troph

s

Chem

oauto

troph

s

25% 25%25%25%

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Cell-Surface Structures

An important feature of nearly all prokaryotic cells is

their cell wall, which maintains cell shape, protects

the cell, and prevents it from bursting in a hypotonic

environment

Eukaryote cell walls are made of cellulose or chitin

Bacterial cell walls contain peptidoglycan, a

network of sugar polymers cross-linked by

polypeptides

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Cell Wall

Prokaryotic cell plasma membranes are

usually covered with a cell wall. Keeps cell

from bursting in hypotonic solutions

Eubacteria cell walls contain peptidoglycan,

a combination of amino acids and sugars.

Cell Wall

Some species have a capsule surrounding the

cell wall. The capsule can provide protection

against immune system cells (phagocytes)

Some bacteria have pili – hair like structures

made of protein, help bacteria to adhere to

surfaces

Some pili are involved in transmitting DNA

between bacteria

Cell Walls

Archaea contain polysaccharides and

proteins but lack peptidoglycan

Scientists use the Gram stain to classify

bacteria by cell wall composition

Gram-positive bacteria have simpler walls

with a large amount of peptidoglycan

Gram-negative bacteria have less

peptidoglycan and an outer membrane that

can be toxic

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Cell Wall Types

There are two main cell wall types. The

differences have important implications in

treating the bacteria with antibiotics

Gram Positive

Gram Negative

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The Bacterial Cell Wall Types

Gram positive

Gram positive cells have thick cell walls,

consisting mainly of peptidoglycan.

Gram positive cells absorb the violet “gram

stain”

Figure 27.3a

(a) Gram-positive bacteria: peptidoglycan traps crystal violet.

Peptido-

glycan

layer

Cell

wall

Plasma

membrane

Fig. 28.8-1

Gram Negative

Gram negative cells have two layers:

A thin peptidoglycan layer

A thick outer layer made of polysaccharides bound

to lipids, similar to plasma membrane

Gram negative cells do not retain the gram

stain, they counter-stain pink

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Figure 27.3b

Outer

membrane

Peptido- glycan layer

Plasma membrane

Cell wall

Carbohydrate portion

of lipopolysaccharide

(b) Gram-negative bacteria: crystal violet is easily rinsed

away, revealing red dye.

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Gram Stain

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External Layers

Capsule

A gelatinous layer found in some bacteria

Aids in attachment

Protects from the immune system

Motility

Most motile bacteria propel themselves by

flagella scattered about the surface or

concentrated at one or both ends

Flagella of bacteria, archaea, and eukaryotes

are composed of different proteins and likely

evolved independently

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© 2011 Pearson Education, Inc.

Video: Prokaryotic Flagella (Salmonella typhimurium)

Figure 27.6

Flagellum

Hook

Motor

Filament

Rod Peptidoglycan layer

Plasma membrane

Cell wall

20 nm

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Flagella

Flagella

Long, helical structures

Composed of the protein flagellin

Involved in locomotion

Motility

Most prokaryotes have a flagella

These flagella are not like eukaryotic flagella,

they are not composed of microtubules

Instead it has:

Basal body that acts like a motor

Hook

Filament

Protein is flagellin

Prokaryotic DNA

Prokaryotes usually have a single, circular

DNA molecule.

Most prokaryotes also have plasmids, small

circular fragments of DNA.

Plasmids can replicate independently or

integrate into the main DNA

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Reproduction in Bacteria

Most bacteria undergo asexual reproduction =

binary fission

Occasionally some bacteria will undergo a

form of sexual reproduction – the plasmid of

one bacteria will be transferred to another

bacteria through the pilus

Internal Organization

Prokaryotic cells usually lack complex compartmentalization

Some prokaryotes do have specialized membranes that perform metabolic functions

These are usually infoldings of the plasma membrane

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Figure 27.7a

(a) Aerobic prokaryote

Respiratory

membrane

0.2 m

Pathogenic bacteria

Some E. coli cause health problems

Clostridium botulinum bacteria produce the

toxin botulism

Clostridium tetanus cause tetanus

Borrelia burgdorferi – bacteria that uses deer

ticks to move from host to host, causes Lyme

disease

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Cause of Disease

Disease caused by bacteria are often

caused by either a toxin released by the

bacteria, or by the response of the host

Bacteria populations can rapidly mutate,

antibiotic resistance can result

The few bacteria that mutate and are

resistant to antibiotics will repopulate the

area with antibiotic resistant bacteria

Commercial Uses

Lactobacillus – used to make yogurt,

pickles, sauerkraut.

Prokaryotic Domains

Domain Archaea and Domain Bacteria

(Eubacteria)

Differences in ribosomes

Archaea does not have peptidglycan in cell wall

Archaea have isoprene units and ether linkages

in the cell membrane.

Domain Bacteria have ester linkages in the cell

membrane and fatty acids

Plasma membrane Table 27.2

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Domain Archaea

Prokaryotic – no nucleus

Extreme bacteria

Methanogens (methane makers)

Extreme halophiles (salt loving)

Extreme thermophiles (heat lovers)

Methanogens example

Discovered in 1983 contains methanococcus jannaschii

[©Stan Watson, Woods Hole Oceanographic Institute]

Pacific Ocean thermal vent

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Halophile example

Dunaliella salina

Thermophile example

Yellowstone NP

Important Concepts

Know the vocabulary in the lecture

What are auto/hetero/photo/chemo-trophs

What are the characteristics of prokaryotes

Which domains are prokaryotic

Know the parts of a prokaryotic cell and their

functions

Know the structure of prokaryotic cell walls,

what they are made of, and the difference

between gram negative and positive,

understand how the gram stain technique works

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Important Concepts

Know how many chromosomes a prokaryote

has and what plasmids are

How do prokaryotes reproduce

What is nitrogen fixation, why is it important

Domain Archaea – three main types

What are the differences between Domain

Archaea and Domain Bacteria (Eubacteria)

How does bacteria cause disease

Antibiotic resistance

Understand eutrophication, including the causes

and effects

To Know for Lab Practical

Be able to identify the three shapes of bacteria,

know their latin names

Be able to identify anabaena.

what are the causes and effects of eutrophication,

What are heterocysts, be able to identfy them

Characteristics of anabaena

What domain does it belong in

Identify Rhizobium and know what element it

fixes, What domain does it belong in

Identify lactobacillus and why is it beneficial,

What domain does it belong in