Exam 19: Archaea

Which genus within Archaea is capable of growth at the hottest temperature recorded of 122°C?

The cytoplasmic membrane of Picrophilus is extremely acid impermeable at very low pH.

Extremely halophilic Archaea stain gram-_________ , reproduce by_________ , and do not form resting stages or spores.

Thermoplasma contains an extremely small genome complexed with a highly basic DNA- binding protein.

What characteristic do mycoplasmas (Bacteria) and Thermoplasma and Ferroplasma (Archaea) have in common?

Approximately_________ of the Methanocaldococcus jannaschii genes have no counterparts in known genes from any group of organisms.

Little is known about the biosynthesis of amino acids and other macromolecule precursors in Archaea.

Why does Halobacterium pump large quantities of K+ cations into its cytoplasm from the environment? What would happen if Halobacterium did not do this?

Most known methanogens are nonhalophilic

An organism that is suspended freely or is attached to suspended particles in the water column is known as_________ .

Most of the Archaea are phenotypically quite similar.

Despite GC pairs having an additional hydrogen bond than AT pairs, hyperthermophilic Archaea generally have a lower GC ratio in their genomes when compared to other heat- sensitive prokaryotes.

Archaeoglobus is a true sulfate reducer that forms a phylogenetically distinct lineage within the Euryarchaeota.

A small, heat- stable DNA- binding protein present in the cells of some Archaea, called Sac7d, binds to the minor groove of DNA in a very specific manner and increases its melting temperature by 40°C.

Compounds that counteract the tendency of the cell to become dehydrated under conditions of high osmotic strength are known as _________.

A compound that is present in molar quantities in the cytoplasm of many hyperthermophilic methanogens and that prevents chemical damage to DNA, such as depurination and depyrimidization, from high temperatures is called __________.

Retinal is found in

Discuss why the periplasm of Ignicoccus is unique among the hyperthermophilic Archaea.

Most halobacteria are motile by means of lophotrichous flagella.

A chemoorganotroph growing optimally at 55°C and pH 2 in complex media would most likely be a member of the genus