Question

Archaea (formerly known as archaebacteria) is one of the three major divisions of living organisms; the other two are eubacteria and eukaryotes. Nanoarchaeum equitans is in the Archaea domain and has one of the smallest genomes known, about 0.5 Mb. How can an organism complete its life cycle with so little genetic material?

Short answer

Answer: Nanoarchaeum equitans can complete its life cycle with a small genome size due to its symbiotic relationship with its host, Ignicoccus hospitalis, from which it obtains essential nutrients. Additionally, the organism efficiently uses its genetic material, containing a streamlined set of genes encoding for essential cellular processes without redundancy or non-coding sequences.

Step-by-step solution

Understanding the Archaea domain

Archaea is one of the three major divisions of living organisms, alongside eubacteria and eukaryotes. They are single-celled microorganisms that often live in extreme environments, such as high temperatures, high salinity, or extreme pH levels. Archaea have unique characteristics that set them apart from eubacteria and eukaryotes, such as differences in their cell membrane and gene transcription machinery.

Genome size and complexity

It is important to note that genome size does not always correlate with organismal complexity. Some organisms with small genomes can have complex life cycles and diverse metabolic pathways. Similarly, larger genomes may not necessarily indicate a more complex organism. The size of a genome is influenced by various factors, such as gene duplication events, non-coding DNA sequences, and the presence of transposable elements.

Nanoarchaeum equitans and its small genome

Nanoarchaeum equitans is a member of the Archaea domain and has one of the smallest genomes known, with a size of about 0.5 Mb. Despite its small genome, this organism can still complete its life cycle. This is mainly due to its ability to rely on its host for some essential cellular processes.

Symbiotic relationship with the host

Nanoarchaeum equitans is an obligate symbiont, meaning it relies heavily on its host, Ignicoccus hospitalis, for survival. The two organisms have a symbiotic relationship, whereby Nanoarchaeum equitans attaches to the host's cell surface and obtains essential nutrients, such as amino acids and lipids, that are required for its growth and reproduction. This reliance on the host allows Nanoarchaeum equitans to have a smaller genome, as it does not need to encode all the genes required for synthesizing these essential molecules.

Efficient use of genetic material

The small genome of Nanoarchaeum equitans contains a limited number of genes, which codes for proteins involved in essential cellular processes such as DNA replication, transcription, translation, and energy production. The organism is able to efficiently use its genetic material to complete its life cycle by having a streamlined set of genes, without much redundancy or non-coding sequences. This allows Nanoarchaeum equitans to maintain a small genome size while still being able to carry out all necessary cellular functions for survival and reproduction. In conclusion, Nanoarchaeum equitans is able to complete its life cycle with a small genome size of about 0.5 Mb due to its symbiotic relationship with its host and the efficient use of its genetic material.