Lesson 6 Taxonomy

The Prokaryotes (Kingdom Monera) are: 1) The eubacteria (so called “true” bacteria - in future lectures, when I use the word bacteria - it refers to the eubacteria unless I state otherwise). Some of the eubacteria cause human disease, and this is why the eubacteria are those bacteria that are of main interest to medical microbiologists. 2) The cyanobacteria (so called and improperly referred to as blue-green algae) - common photosynthesising bacteria often noted as the green scum on ponds in summer months. 3) The purple photosynthetic bacteria, these perform photosynthesis but they do not use chlorophyll, they use special purple pigments instead, they are found in brine ponds for instance. 4) the Archaebacteria, a group of evolutionarily ancient bacteria which are adapted to living in extreme environments such as high salt, intense cold, high temperature, high acidity etc ALL the other Kingdoms contain eukaryotic organisms:



The Kingdom Protista.

These are a diverse set of organisms Algae - fresh and saltwater, single cells to simple multicellular photosynthesising organisms. Autotrophs, most have cell walls. Slime molds- they are NOT fungi, look like fungi but can also be animal or even plant-like in morphology. Heterotrophs Protozoa, a diverse group of single celled creatures that look and act like animals often, but are not, includes amoeba, paramecia etc, they are heterotrophs (some have autotrophic algae as symbiotic partners). Some protozoa cause human disease. Some protists have plant and animal-like characteristics and are hard to classify - the Euglenoid protista are Heterotrophic and Autotrophic.

The Kingdom Fungi.

Non photosynthesising single celled to multicellular organisms most of which have cell walls. Heterotrophs. Includes yeasts (which are unicellular) and mycelial (filamentous) organisms such as bread mold and the mushroom forming fungi. Some fungi cause human disease, some are important in food preparation

The Kingdom Plantae

Autotrophs. Multicellular photosynthesising organisms with cell walls. Trees, shrubs, bushes, grasses, moss, ferns etc.

The Kingdom Animalia.

Heterotrophs. Complex multicellular organisms of diverse types, no cell walls, showing characteristic irritability and movement. Some cause human disease (parasitic infections, worms etc or act as vectors for other disease causing organisms).


Viruses are not classified by using the Binomial naming system and do not belong to any of the five kingdoms. Viruses are not cellular and are dependent on host cells for their replication. Viruses are classified in two different ways: 1) according to their structure - genetic (DNA or RNA?) and physical (shape etc) – this scheme is favoured by scientists doing fundamental work. 2) according to the type of disease they cause, this scheme is favored by medical workers who need to correlate given viruses with given diseases.

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