11 The Diversity of Bacteria and Archaea

6,000

Prokaryotes (Eukarya, Bacteria) are the most diverse in terms of shape, metabolism, habitats

Out of a million species estimated to exist, only [__] are identified → 950 genera

• most not isolated

• metagenomics and new molecular techniques aid in discovery and characterization » can make predictions from genes

metabolic diversity

Ability to use different substances as carbon and energy sources

Allows microbes to live in diverse environments

single

Members of the domain Bacteria and Archaea BOTH:

• are [__]-celled organisms

• lack membranes and membrane-bound organelles

• rigid cell walls

  • peptidoglycan in Bacteria

  • pseudopeptidoglycan in Archaea

• have similar shapes

• move by means of flagellum

• multiply by binary fission

however, Archaea differ in how they can survive in extreme environments (w/ exception of Methanogens)

chemolithotroph

Organism that harvests energy by oxidizing inorganic chemicals. eg. H₂

Anaerobic [__]s, such as methanogens, utilize inorganic compounds like H₂ for energy but don’t have oxygen as final electron acceptor (uses CO₂ instead)

methanogens

Archaea that are anaerobic chemolithotrophs » generate methane from H₂ (oxidizes it) and CO₂ (electron acceptor) from environment.

The exception to Archaea thriving in extreme environments

Extreme Halophiles

Prokaryotes, primarily Archaea, whose members thrive in highly salty environments

Extreme Thermophiles

Prokaryotes, typically Archaea, who thrive in high temperature environments (typically boiling)

Bacteria

Members of this domain are commonly responsible for human infections

nutrients

Microbes can be found in every type of habitat that supports every life.

i.e., microbes can exist so long as they have the required [__] for growth and can withstand the environmental conditions

• extreme environments

• terrestrial environments (soil, air)

  • water evaporated in the air has microbes in them

• aquatic environments (open sea, lakes, streams, ponds, marshes and wetlands, hot springs, arctic ice sheets)

in addition to microbes living in humans, they can also be associated with insects, plants and animals

Thermus aquaticus

Extreme hot environments include:

• boiling pools

• hot springs

• hydrothermal vents → can be 120C (250F)

  • worms associated with these vents have bacteria in their folds

  • eg. Taq polymerase found here in [__]

red bacteria

Extreme cold environments include:

• glaciers and snow fields

  • can find [__] here » photosynthetic and produces red pigment

• Antarctic ice sheets → 12C (10F)

Halobacterium

Extreme high salt environments include:

• Great Salt lake, Dead Sea, soda lakes

  • where extreme halophiles reside (mostly in 5-32% salt)

  • bacteria, algae, protozoa typically require 9% salt conc.

• Owens lake (Sierra Nevada)

  • reddish color due to the salt-loving bacteria [___]

Anoxic extremophiles

Extreme highly basic (alkaline, hypersaline) environments include:

• Mono Lake in California

  • has [__]: extremophiles that can live without O₂

Sulfolobus

[___] is a bacteria that thrives in sulfuric-rich, acidic hot springs and soils

• uses sulfur as energy → oxidize sulfur to sulfuric acid

• requires pH between 1-6

• grow above 50C to 85C

Sheathed bacteria

Bacteria residing in aquatic environments lack steady supply of nutrients.

Mediates this by forming chains of cells within a tube → multiple bacteria in structure of sheath

• sheaths protect and help bacteria attach to solid objects

• sheath enables them to share nutrients within tube

• Gram-negative bacteria

eg. Sphaerotilus, Leptothrix

Look like filamentous and long strings of cells

Prosthecate bacteria

Bacteria residing in aquatic environments lack steady supply of nutrients.

Mediates this by having extensions that provide increased SA for nutrient absorption; some extensions also allow attachment

eg. Caulobacter

Caulobacter

Bacteria of this genus are Prosthecate bacteria;

during replication:

• flagellum → sported by daughter cell; uses it to swim away from parent cell

when the daughter cell finds its own location, it:

• loses its flagella

• sprouts a stalk → long extension that has the holdfast structure

  • holdfast » enables them to stick to surfaces. specifically one with nutrients → utilizes such nutrients for for reproduction as well

Bdellovibrio

Bacteria residing in aquatic environment that is a highly motile Gram-negative curved rod

Preys on other bacteria, such as E. coli and other Gram-negatives

» attaches to bacteria and get through outer membrane

→ flagellum propels them toward prey (spinning motion) and enzymes enables them to creates holes in their cell wall

» get into periplasmic space → feed on bacteria

» grow and reproduce inside host

» lyse cell with progenies

Staphylococcal

Animal bodies provide a variety of ecological habitats for bacteria

The skin is one of them

» typically dry; inhospitable to many microbes

» [___] species → significant component of skin flora

eg. [__] epidermidis most common organism; some carry S. aureus

Bifidobacterium

Animal bodies provide a variety of ecological habitats for bacteria

The Mucous membranes (Respiratory, genitourinary, intestinal tracks) are one of them

» Bacteriodes → found in mouth, GI, and genital tracts→ most abundant bacteria in the gut and genital tract

» [__] → found in GI tract and can cause infections, but provide beneficial early exposure/immunity to babies who are breastfed

Bioluminescent bacteria

Bacteria that have symbiotic relationships (mutualistic symbiosis) with:

• certain fish and squid (helps with camouflage and confuse predators and prey)

• other animals for food and protection

eg. Photobacterium, Vibrio

a. [___] b. flashlight fish that contains [__] under its eye

Mutualistic symbiosis

Good symbiotic relationship; benefits both the animal and bacteria

eg. flashlight fish provides protection for bacteria and gets all the food they want form the fish

fish gets light from the bacteria to see and hunt for food

aphids

These organisms live in association with fungi and bacteria:

» Ants lives in association with fungi → cultivates fungal garden to grow on substrate

the fungi will breakdown this substrate to a form that the ants can use as a source of food

» [__] live In association with bacteria → in the gut of this [__], bacteria exist

bacteria synthesizes sap (their only source of food) into essential nutrients they need

Agrobacterium

Bacteria that associate with plants.

Produces plant tumors to gain nutrients, which are often fatal to the plant → due to their Ti (tumor-inducing) plasmid

[__] therefore is a plant pathogen

Rhizobium

Bacteria that associate with plants.

Has a mutually beneficial relationship with legumes → fixes nitrogen to be used as a nutrient source for plant

initiates formation of root nodules on plant roots

Plants grow faster when they are infected by [__]