What is not bacterial or eukaryotic?

This article "Biology's 'dark matter' hints at fourth domain of life"^[1] from the New Scientist suggests that the current scheme of bacteria, archea, and eukaryotes might need some updating.  This would certainly suggest that the IB Biology syllabus that does not even mention domains but only kingdoms, is also behind the times.

Craig Venter's team, who produced the first synthetic genome in 2010, has worked on the metagenomics of sea life to find new genome signatures which do not resemble any other life forms so far.  Others mentioned in the article suggest that the new genome information may not be from another life form but just diversified life adapted to novel conditions.  This is the eternal debat between splitters and lumpers.

Changes in scientific thinking do occur over time, producing what TOK students know to be paradigm shifts.   Considering that Aristotle, 2400 years ago, described only two kingdoms of life: plants and animals. Linneaus kept the two kingdoms and these held even through the discovery of single celled organisms by van Leeuwenhoek, until 1866 when Haeckel proposed 3 kingdoms: Protista ( single celled organisms), Plantae and Animalia.  A fourth kingdom was proposed in 1925 by Copeland and in 1969 the five kingdoms  we recognize today (Monera, Protista, Fungi, Plantae and Animalia) were sponsored by Whittaker. Woese suggested 6 kingdoms by splitting the Monera into the Eubacteria and Archaebacteria which later supported the 3 domains of Bacteria, Archea and Eukarya in 1990.  A further restructuring, in 2004 by Cavalier-Smith, made 6 kingdoms by splitting the Protists into the Protozoa and Chromista.^[2]

Here is an extract from this article that would suggest this paradigm shift to be a possibility.

"If Eisen's gene sequences did turn out to belong to a new domain of life, it wouldn't be the first time the tree of life has had to be redrawn. Until the 1990s, it had just two branches: one for eukaryotes – animals, plants, fungi and some other strange forms, including the slime moulds – and one for everything else. Then, gene analysis revealed that the "everything else" branch could be divided into two domains: bacteria and archaea."

IB biology students only need to know the classification of 2 organisms in two kingdoms.

5.5.2- List seven levels in the hierarchy of taxa—kingdom, phylum, class, order, family, genus and species—using an example from two different kingdoms for each level.

I would use this article to open a discussion about the need for classification of organisms or to introduce the prokaryotes and eukaryotes.

Students might find the seemingly small representation of the 3 kingdoms; Animalia, Plantae, Fungi, quite surprising but this is good to indicate how little we really know the living world around us.  Large animals and plants are obviously very visible while the bateria are not.  Now there might be another domain still undiscovered.