All prokaryotes face a crucial energy dilemma at the cytoplasmic membrane. Each
ID: 191764 • Letter: A
Question
All prokaryotes face a crucial energy dilemma at the cytoplasmic membrane. Each cell must expend energy to maintain a chemiosmotic potential, which is used to drive basic cellular processes. Known archaeal groups can dominate or out-compete bacteria in ecological niches in which chronic energy stress is a feature, including environmental stresses (temperature, acidity and salinity) and low energy availability. Please explain Adaptations to energy stress dictate the ecology and evolution of the Archaea" by David L. Valentine, 2007. Nature Reviews Microbiology 5, 316-323 as a guide. (10 pts)Explanation / Answer
Answer:
One important distinction between archaea and bacteria is the chemical structure of lipids composing the cytoplasmic membrane. Bacteriall membrane typicalle consists of fatty acids exterified to a glycerol moiety, whereas archael lipids typically consist of isoprenoidal alcohols that are ether linked to glycerol.
Stereochemical configurations about the glycerol moiety are also different. Archael membranes are less permeable to ions than bacterial membranes, and tetra-ether based membranes are less permeable than diether-based membranes.
These membranes reduce the amount of futile ion cycling in vivo and provide an energetic advantage to archaea - less energy is lost during maintenance of chemiosmotic potential.
The advantages of archaeal membranes have been clearly shown in hyperthermophiles, halophiles, acidophiles and lipid vescicles derived from these cells, and it seems reasonable to simply extend this principle to include other archaea.