Although kingdom Monera was readily adopted and later accepted as part of a five-kingdom system (whereby American biologist Robert H. Whittaker separated the fungi into their own kingdom), in the purview of some researchers, Monera remained an unsatisfactory division.
Her 1982 book Five Kingdoms, written with American biologist Karlene V. Schwartz, articulates a five-kingdom system of classifying life on Earth animals, plants, bacteria (prokaryotes), fungi, and protoctists.
Still other researchers disagreed with the domain system, however, and in 1998 British zoologist Thomas Cavalier-Smith presented yet another classification scheme, the six-kingdom system, which contained kingdom Bacteria, with two subdivisions: Eubacteria and Archaebacteria.
The three-domain system has largely replaced the previous five-kingdom system of American biologist Robert H. Whittaker, which is based on morphology (e.g., mode of nutrition) rather than phylogeny (the history of the evolution of a species or group).
Synergistic effects of attenuated Salmonella and our inter-kingdom system allow the precise expression of Diphtheria toxin A chain (DTA) gene in tumor microenvironment and eradicate large established tumors in immunocompetent animals.
However, many scientists now consider this five-kingdom system outdated.
When we moved past characteristics of living things and on to the six kingdom classification system, I was less surprised to note that few of my students knew we were animals.
The Belgian provinces also complained that they were underrepresented by the Kingdom's system of government, where 55 Belgian deputies were allocated to represent 3.5 million people, while an equal number of Dutch deputies represented just 2 million.
This protein, apparently involved in adhesion and virulence, reveals the existence of a possible new inter kingdom signalling system and suggests that the human microbiome should be involuntarily exposed to the evolutionary pressure of benzodiazepines and related molecules.
The modified Whittaker five-kingdom classification system is perhaps the most comprehensible and biologically based way to unambiguously organize information about all groups of living beings.
Besides serving as an inexpensive, reliable, versatile and easy-to-assay cross-kingdom reporter system, the potential of having mammalian cells produce non-ribosomal peptides, preferably ones with biopharmaceutical activities, may provide novel treatment opportunities in future gene- and cell-based therapies.
