chapter 27: prokaryotes - structure, function, diversity, evolution, impact

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impact

PROKARYOTES (CHAPTER 27)

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactStructure of Prokaryotes


Gram positive vs Gram-negative prokaryotes

Why are they called “gram-positive” and “Gram-negative”?

Bacteria come in two flavors:


A simple procedure used to stain bacteria:

Gram Staining

The thick peptidoglycan cell wall of gram-positive bacteria prevents the stain (crystal violet-iodine) from leaving the cell when decolorization is carried out.


Penicillin

Taking advantage of the peptidoglycan cell wall:

Antibiotic that inhibits enzyme DD-transpeptidase, which is involved in building and rearranging the cell wall.

DD-transpeptidase with penicillin bound:

penicillin


CapsulesCapsules surround cell walls of many prokaryotes.

- Composed of polysaccharide or protein

Function:

Structure:

- Allows bacteria to bind to other bacteria or to another substrate like your cells.

- Protection from immune system


Fimbriae and Pili

Function:

- Allows bacteria to bind to other bacteria or to another substrate like your cells.

- Sex pili are specialized pili used during conjugation.

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactMotility of Prokaryotes

Flagella

- 50% of prokaryotes capable of directional movement.

- Flagella are most common, but not the only means of motility

- NOT covered by plasma membrane like in eukaryotes.

- Basal apparatus (motor proteins) cause flagella to ROTATE, not whip like in eukaryotes.

The very different structures of the prokaryotic and eukaryotic flagella is a clear example of…

Is this bacterium gram + or gram -?

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactMotility of Prokaryotes

Taxis

Taxis = to move towards or away from a stimulus

Chemotaxis – towards (positive) or away (negative) from a chemical.

Phototaxis – towards (positive) or away (negative) from light.

Bacterium exhibiting positive chemotaxis

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactInternal and Genomic Organization - membranes

Membrane organization reminiscent of mitochondria and chloroplasts


Single circular chromosome in nucleoid region plus plasmids

Internal and Genomic Organization - membranes

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactReproduction and Adaptation in Prokaryotes

- Binary fission (asexual) every 1 to 3 hours (some only 20 min)

- ENDOSPORES

- Formed by certain bacteria when environment goes south (lacking a nutrient, etc…)

- Highly Resistant cells

- Bacterium replicates chromosome and surrounds with tough wall.

- Remainder of cell breaks down- Most endospores survive boiling and can persist dormant for 100’s of years

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProkaryotic Nutritional Classes

- There are prokaryotes in every nutritional class:

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProkaryotic Metabolic Relationships to O2

Obligate (strict) aerobes

Facultative aerobes

Obligate (strict) anaerobes

- Use oxygen for cell resp. CANNOT be without it

- Use O2 if present, switch to fermentation in absence of O2

- Poisoned by O2

- Two types:

1. Fermentation – bacteria that only do fermentation

2. Anaerobic respiration – use substance other than O2 as final electron acceptor like nitrate (NO3-) and sulfate (SO42-)


Nitrogen Fixation

N2 NH4+

Nitrogen fixing bacteria take atmospheric nitrogen (N2) and can convert it to NH4 (ammonium) for use in its amino acids and nitrogenous bases. Excess is secreted and used by plants as shown to the right…

Nitrogen Metabolic

THIS IS THE ONLY WAY NITROGEN CAN ENTER THE ECOSYSTEM…THIS IS WHERE ALL YOUR NITROGEN COMES FROM!!

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProkaryotic Metabolic Cooperation

Colonial Cooperation: Certain bacteria like the cyanobacterium Anabaena in colonies. Photosynthetic cells are mixed with heterocyst cells, which fix nitrogen only since O2 produced during photosyn. inhibits nitrogen-fixing enzymes.


Biofilms: Surface coatings of cooperating bacteria. Above, dental plaque, a biofilm that forms on tooth surfaces.

Channels form in the biofilm to allow nutrients and waste to enter and exit the interior of the film respectively.

Prokaryotic Metabolic Cooperation

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProkaryotic Phylogeny

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactComparing the three domains:


Archaea Bacteria

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactArchaea Bacteria

Extremophiles - “lovers” of extreme conditions

1. Extreme Thermophiles

- thrive in hot environments

Ex. Sulfolobus – genus that live in sulfur-rich volcanic springs pushing 90°C.

2. Extreme Halophiles

- thrive in high salt environments

3. Methanogens- Obligate (strict) anaerobes – poisoned by O2

- Many species live in swamps and marshes

- Use CO2 to oxidize H2, releasing CH4 (methane) as waste.


Eubacteria

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactEubacteria

Fig 27.13 in book

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProkaryotic Symbiotic Relationships

Symbiosis

Hst – larger organismSymbiont – smaller organism

Mutualism (+/+)

Commensalism (+/0)

Parasitism (+/-)

Three Forms:

Human Intestinal bacteria

Glowing below eye of flashlight fish is organ containing bioluminescent bacteria. Light used to attract predators and mates. Bacteria gets nutrients from fish.

– relationship b/w organisms of different species in direct contact

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactPathogenic (parasitic) Prokaryotes

- Cause about half of all human diseases**2 to 3 million die a year from lung disease caused by Mycobacterium tuberculosis

**2 million others die of diarrheal disease caused by prokaryotes

Lyme disease- Most widespread pest-carried disease in United States

- Tick carries spirochete Borrelia burgodorfi

- The tick is called a vector because it transmits the disease as would a mosquito that transmits the protist that causes malaria.

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactPathogenic Prokaryotes

ExotoxinsToxic proteins secreted by pathogenic bacteria

Ex. Cholera

- Life threatening diarrhea

- Caused by Vibrio cholera

Exotoxin called cholera toxin (CTX) causes intestinal cells to secrete Cl- into gut and water follows by osmosis

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactPathogenic Prokaryotes

Endotoxins-Toxic lipopolysaccharides (glycosylated phosopholipids) found in outer membrane of Gram negative bacteria.

- Released when cell dies and outer membrane breaks down

Ex. All members of genus Salmonella- Typhoid fever (fecal oral route)

- Food poisoning (esp chicken)

Typhoid bacillus(Salmonella enterica)

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProkaryotes in Research, Technology and Society

- Convert milk to cheese / yogurt

- E. coli in gene cloning

- Agrobacterium tumefaciens to make transgenic plants

- BioremediationUse of organisms to remove pollutants from the environment

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactProtists (Chapter 28)

1. More structural and functional diversity than any other group of organisms…

2. Most are unicellular, some colonial and multicellular…

3. Most nutritionally diverse eukaryotes

C. mixotrophs – combine photosyn with hetertrophic nutrition

A. photoautotrophsB. heterotrophs


Broken into three general categories based on ecological context:

1. Photosynthetic (plant-like) protists

3. Absorptive (fungus-like) protists

- algae

2. Ingestive (animal-like) protists

- protozoans

Protists


How did such incredible diversity arise?

Protists

Many species resulted from two rounds of endosymbiosis…

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4

Phylogenetic tree showing the major clades of protists.


A complete branch of a phylogenetic tree. Above how many clades are highlighted?

What’s a clade?

Two, the blue and the red because these are complete branches. The green is not complete.


Let’s examine a handful of these clades…

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Euglenozoa Fig. 28.8

Characterized by spiral or crystalline rod within flagella in addition to 9+2 arrangement of microtubules.

Cyrstalline structure has unknown function.


Phylum kinetoplastid

- Causes sleeping sickness

- Spread by African tsetse fly- Fatal if untreated

Ex. Genus Trypanosoma

- Evade immune system by repeatedly changing the proteins on the surface of the cell


Phylum euglenid

- Found in freshwater

- Photoautotroph if sunlight available otherwise heterotroph by absorbing nutrients from environment (mixotroph)

Ex. Euglena

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Alveolata Fig. 28.8

Characterized by sacs below membrane called alveoli having yet unknown function


Phylum dinoflagellates

- Abundant as both marine and freshwater phytoplankton

- Bloom (explosion of growth) can cause “red tide”

Kingdom Alveolata

Phytoplankton – phyto = photosynthetic, plankton = “free-drifting”

- free-drifting photosynthetic organisms (cyanobacteria is also a large part of phytoplankton)

- Secrete toxins that bioaccumulate in molluscs making them dangerous to eat

- Have internal “plates” of cellulose giving its characteristic shape…


Phylum Ciliates

- Obviously use cilia to move and feed

- Can have more than one of each

Kingdom Alveolata

Two types of nuclei

- Large (macro) nucleus

- Smaller (micro) nucleus

Ex) Paramecium


Phylum Ciliates

- Arranged in small units each having many duplicates of a single gene

Kingdom Alveolata

Macronucleus

- Contains dozens of copies of genome

- Genes are not on chromosomes (they don’t have chromosome)

- The gene products (i.e. proteins) control daily functions like feeding, waste removal, etc…


Phylum Ciliates

- Food vacuoles fuse with lysosomes

Kingdom Alveolata

Feeding

- Mainly on bacteria, which are moved through oral groove and phagocytosed at “cell mouth” into food vacuoles.

- Undigestable material is egested when lysosomes fuse with cell membrane


Phylum Ciliates

Conjugation

Kingdom Alveolata

Reproduction

- Mostly asexually by “binary fission”

- two organisms exchange haploid micronuclei (see fig 28.12b above and use book for more detail)

- Genetic diversity, NOT REPRODUCTION


Phylum Diatom (Bacillariophytes)

Kingdom Stramenopila

- Unicellular Algae

- Protection from predators

- glass-like silica based cell wall as shown in figure

- Withstand pressures up to 1.4 million kg/m2 (pressure applied by the leg of a table with an elephant standing upon it)


Phylum Diatom (Bacillariophytes)


Reproduction

- Sexual reproduction is not common, but does occur

- Usually asexually by mitosis

- Estimated 100,000 species

Diversity

- Major component of phytoplankton in oceans and lakes


Phylum Golden Algae (chrysophytes)


(chrysos = golden)

- Freshwater and marine plankton

- Contain yellow/brown cartenoid pigments

- All obviously photosynthetic, some species mixotrophs

- Most unicellular, but some, as shown, are colonial

Dinobryon


Phylum Brown Algae (phaeophytes – guess what phaeo means…)


- All are multicellular and most are marine (salt water – ocean)

- Largest and most complex algae (its what you call seaweed)

- Common along temperate costs like ours

Kelp


Phylum Brown Algae


- The body of the seaweed that is plant-like

Thallus Kelp

- Basically, the holdfast, stipe (stem-like) and blades (leaf-like) (see above)

- root-like structure at base solely for anchoring, not absorption like roots of plants

Holdfast

Sea palm (Postelsia)

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactPhylum Brown Algae


This is important to understand because as you might guess, since plants evolved from multicellular algae, they also do this.

Life-cycle: Alternation of Generations

- The two generations are structurally different as opposed to being isomorphic

Heteromorphic

Laminaria (a brown algae)

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Cercozoans and Radiolarians

- Amoeba with threadlike pseudopods

- Amoeba is a general term for a protist that uses pseudopodia to move and feed. There is no one clade or kingdom that consists of amoebas

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Cercozoans and Radiolarians

Foraminiferans (Forams) Radiolarian

- Named for porous shells called tests

- Foramen means “little hole”

- Organic molecules hardened with CaCO3

- Pseudopodia extend through pores of shell and fx in test formation, swimming and feeding

- Pseudopodia called axopodia

- Tests made of silica

Both of these phyla consist of amoebas because…

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Amoebozoans

- Amoeba with lobe shaped rather than threadlike pseudopods belong to this clade:

Now this amoeba belongs to the above kingdom…


Phyla: Gymnamoeba

Phagocytosis of a ciliate:


Phyla: Slime Molds (mycetozoans)

Two major types:

Were once thought to be fungus hence the name, but molecular evidence has revealed convergent evolution

1. Plasmodial Slime Molds

2. Cellular Slime Molds

They in part by their life cycles…



Plasmodial Slime Mold Life Cycle



Cellular Slime Mold Life Cycle

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Rhodophyta

Rhodo = red

Red Algae

Red due to pigment known as phycoerythrin, which masks chlorophyll

Most large and multicellular, living in tropical waters

Alternation of Generations

Chapter 27: Prokaryotes - structure, function, diversity, evolution, impactKingdom Chlorophyta

Chloro = green

Green Algae

Much like plants, systematics has shown close relationship b/w green algae and plants as you would expect…

Two groups

1. Chlorophytes

- More than 7,000 species, most in fresh water- Simplest are unicellular

- These are the ones that live in mutualism with fungus to form lichen

Watermelon snow showing the incredible diversity of chlorophytes

- Chlorophytes and Charophyceans

*Charophyceans and most related to land plants and are discussed at beginning of Ch. 29 with plants


Chloro = green

Green Algae

Larger size and complexity arose via:

1. Colony formation (ex. Volvox) and multicellular filament formation.

2. Repeated division of nuclei without cytoplasmic division (ex. Caulerpa)

3. True multicellular forms with cell division and differentiation (Ex. Ulva)


Chloro = green

Green Algae

Complicated life cycle of asexual and sexual stages:

Syngamy = fusion of gametes, aka fertilization/conception

chapter 27: prokaryotes - structure, function, diversity, evolution, impact

Documents

prokaryotes structure

chloroplasts chapter

impactprokaryotes chapter

certain bacteria

remainder of cell

bacterium gram

positive chemotaxischapter

tough wall