L18: Extremophiles: Alkaliphiles + Deinococcus

Question 1

What are 4 general facts about alkaliphilies

Answer 1

1. high pH optimum >9
2. obligate alkaliphiles cannot grow less than 7
3. maintain internal ~8.0
4. Alkalitolerant organisms grow at high pHs
   but have normal pH optimums of ~ 7

Question 2

Describe the habitat

Answer 2

• highly distributed
• require alkaline environment and Na+ for growth
• Carbonate-rich springs and alkaline soils like cyanobacteria, Bacillus spp
• soda lakes => produce haloalkaliphiles
  ===> large amount of sodium carbonate and NacL with high buffering capactiy to maintain high pH
  ===>unlimited biocarbonate photosynthesis, warm ambient
  temperatures (30-35ºC), and high intensity of illumination
  ======> makes large cyanobacterial blooms and other phototrophs

Question 3

What are Haloalkaliphiles

Answer 3

-Isolated from relatively rare alkaline hypersaline lakes (> 20%
NaCl)
-Predominately Archaea and include Natronobacter,
Natronococcus and Halobacterium with cyanobacteria present

Question 4

Describe the conditions of the soda lake ecosystem

Answer 4

• cyanobacterium Spirulina has high
  concentrations of carotene, giving it a
  distinct pink color

Question 5

List physiological adaptations of alkaliphiles

Answer 5

Contain adaptations to their cell envelopes
- Internal pH is around 8
- Internal cellular machinery functions in this relatively neutral environment i.e.,
cytoplasmic enzymes, ribosomes ..

• Exoenzymes are highly adapted to function at alkaline pHs

Cell wall highly adapted to protect cytoplasmic enzyme (contain high conc. of acidic
polymers, hexosamines (amino sugars))

Question 6

How do alkaliphiles make ATP?

Answer 6

• use a sodium motive force to produce energy, power the flagellar motor
• Proton motive force is maintained by trapping H+ in a gel
  exterior to the membrane?

Question 7

Discuss spirulina applications

Answer 7

Only cyanobacterium consumed as
human food!
§ Is considered a health food in the West,
lots of amino acids, low level of nucleic
acids!
§ Thought to enhance performance, sort
of a natural performance enhancing
drug!
§ Spirulina has also been targeted by the
biotech industry for producing essential
amino acids and vitamins because of its
high photosynthetic yield!

Question 8

What are applications of alkaliphiles

Answer 8

• wahing powders, 40% global enzyme productions
• using amylases, , xylanases,
  pullulanase ==> produce cyclodextrins to deliver eyedrops

Question 9

What is a very resistant extremophile, how disovered and grown

Answer 9

Deinococcus radiodurans and several other Deinococcus spp.
are extremely resistant to ionizing radiation.

How this bacterium can grow under chronic gamma radiation
[50 grays (Gy) per hour] or recover from acute doses greater
than 10 kGy is under intensive investigation.
§ Deinococcus radiodurans was originally isolated in 1957 when
it was found in a can of ground meat that spoiled despite
having been sterilized by radiation.
§ Deinococcus spp. have been isolated worldwide from
locations rich in organic nutrients, including soil, animal
feces, and processed meats, dry, nutrient-poor
environments, including weathered granite in a dry Antarctic
valley, room dust, irradiated medical instruments …

Question 10

Name resistans, chartacterists and adaptations of deinoccosus

Answer 10

§ Stains Gram-positive but is really Gram Negative, red-pigmented, nonmotile bacterium
§ Extremely resistant to a number of agents and conditions that damage DNA, including
ionizing and ultraviolet (UV) radiation, dessication and hydrogen peroxide (H2O2)…
§ D. radiodurans’ ionizing radiation resistance may be incidental, perhaps an adaptation
to a common physiological stress, dehydration and desiccation?
§ Can withstand 1.5 million rads à a 1000x more than any other life form on Earth,
3000x that of humans
§ Most cells, including human cells, can mend only very few breaks in their DNA
§ Most bacteria 3 to 5 breaks in DNA
§ D. radiodurans > 200 breaks

Question 11

How does D. radiodurans withstand such damaging radiation??

Answer 11

Genome Sequencing Project of Deinococcus radiodurans
- All systems for DNA repair, DNA damage export, desiccation and starvation recovery, and genetic redundancy are present in one cell
- high efficnecy DNA repair + redudnacy
- e mechanism to transport out damaged nucleotides
many DNA repeats elements throughout
- NO unique enzymes that repair = no magic

Question 12

What are recent theories put forth about Conan the Bacterium

Answer 12

1. donut genome
2. manganese protein protection plant
3. magical radiation resistant protein plan: Ddra (DNA damage responses A protein)

Question 13

Expplore donut idea + phases