The term achae comes from Greek meaning ancient. There is a probability that Archaebacteria evolved from a common ancestor like eukaryotes and Bacteria but there is a close relationship between Archaebacteria and eukaryotes than Bacteria. Margulis & Schwartz (1998) state that Archaebacteria are single celled and complex organisms.
There are many features that distinguish Archaebacteria from Eubacteria. They include:
- They have a unique lipid bilayer of cell membranes.
- No polypeptide in their cell walls.
- Their ribosomal protein is more similar to eukaryotes.
- Their RNA polymerase in a more similar manner to eukaryotes.
According to Margulis & Schwartz (1998), Archaebacteria grow in extreme habitats like acidic aquatic environments, anaerobic environments, salt flats and hot boiling water (springs). Archaebacteria are further subdivided into three groups, that is: thermoacidophiles, extreme halophiles and methanogens.
- Just like their names suggest, the bacteria can withstand very hot temperatures and low PH.
- They can survive temperatures of up to 80 ° C and PH of 2.
- Many are chemosynthetic.
- They are mostly found near hot springs and hydrothermal vents.
- They are anaerobic bacteria that produce methane gas
- Are found in, bogs, sewerage treatment plants and intestinal tracts of ruminant animals like cattle.
- Ancient methanogens are a source of natural gas.
They use Hydrogen (H2) to reduce carbon dioxide (CO2) to methane gas (CH4). Exposure to oxygen may destroy them hence this principle is applied in aeration of sewerage in water treatment facilities.
- They thrive in areas with high salt concentration like salt lakes and or pools of sea water
- They can survive in conditions that are ten times the salt concentration of the sea.
Pyrococcus furious is an example of Archaebacteria that lives in boiling water. It dies if the water temperature drops below 70° C. the organism can not stand oxygen and dies on exposure. Pyrococcus furious breathes Sulfur and exhales hydrogen sulfide. It can be commonly be found near undersea vents (Margulis & Schwartz, 1998).
It is a very large grouping of complex and single celled organisms. They are far much extensive than Archaebacteria. This group is made up most bacteria and commonly found everywhere hence very familiar with many people. Kingdom Eubacteria is made up of the following groups: Actinomycetes, Chemoautotrophs, Cyanobacteria, Endospore forming, bacteria, Enteric bacteria, Mycoplasmas, Myxobacteria, Nitrogen fixing bacteria, Phototrophic bacteria, Pseudomonads, Rickettsias and chlamydias, and Spirochaetes.
Nitrogen Fixing Bacteria
- The widely studied of this group are the mutualistic species that live in root nodules of leguminous plants like beans.
- They absorb atmospheric Nitrogen (N2) and convert it to a form that can be utilized by legumes, that is, nitrates and nitrites.
- Apart form the mutualistic species, there also exist free-living species.
- Its typical genera are Rhizobium and Azotobacter
- Rhizobium leguminosarum is a bacterium found in root nodules of legumes that fixes atmospheric nitrogen.
Little was known about Enteric Bacteria because they are facultatively anaerobic and difficult to culture. Escherichia coli (E. coli) is the most well known of Enteric Bacteria and is described as below:
- Lives in human small intestines
- It experiences a symbiotic relationship in human small intestines through producing vitamin K for human body.
- They are gram negative.
- Some are harmless and very beneficial, E .coli, in particular.
- Some E. coli and some other genera are very pathogenic.
- The other genera is made up of Salmonella that is responsible for Salmonella poisoning
Vibrio cholera is another genera, that is responsible fro cholera (Margulis & Schwartz, 1998).
- They are different from other Eubacteria for they lack cell walls.
- Basically, they are a mass of very small protoplasm (0.10-0.25 µm), arguably some of the smallest of all cells
- For most part, they are animal and saprobic but in some areas like South Florida, they have been implicated in lethal yellowing of palms.
It is a diverse group of bacteria. One of its genus is Pseudomonas:
- Are found in virtually all soil and aquatic habitats.
- Are characterized by rod-shaped, Gram negative cells that have flagella tufted at one end (lophotrichous).
- Are chemoheterotrophs.
- Many bacteria of them (not cyanobacteria) produce flagella.
- Neither cyanobacteria nor bacteria produce cilia
- Both of tem produce a mucous or slime coat for protection
- The flagellum is made up of flagellum protein known as flagellin and epsilon-N-methyl lysine.
Kingdom Protista members are the simplest of the eukaryotes. Protists are an unusual group of organisms that were brought together due to the fact that they really did not appear to belong to any other group. In this group, there are some organisms that move around and act like animals whereas others Protists perform photosynthesis just like plants do. Nevertheless, protists are neither animals nor plants. Some individuals think that they are fungi even though they are not. Some scientists see Kingdom protistsa as a home for leftover organisms that could not be classified elsewhere (Margulis & Schwartz, 1998).
Some of the characteristics of Protists are: They can be heterotrophic for animal like or autotrophic for plant like (they contain chloroplasts and make there own food), they mostly live in water although some live in moist soil or even surprisingly in human body, mostly unicellular though some like algae are multicellular, all of them have a nucleus therefore eukaryotic and they reproduce either sexually or asexually.
In Linnaeus’s original two-kingdom scheme, there was no clear classification for prorists. This served as one of the many causes for reorganizing the classification system and gave birth to the five-kingdom classification. This kingdom is very diverse because in it, there exists the ancestors of all the other eukaryotic kingdoms. The animal like prorists are also called Protozoa, meaning, “first animal” while the plantlike prorists are also called Algae.
Margulis & Schwartz (1998) assert that within Kingdom Prorista, there are numerous phyla that are further subdivided into main groups. Animal like Prorists are grouped according to the way they move and plant like prorist are grouped based on how they carry out photosynthesis. On the other hand, fungus like prorists are looked at as either parasites, decomposers or heterotrophs.
Animal like prorists (Protozoans) are grouped in four phyla that are further classified into their way of movement. The classifications are:
- They move using one or two flagella
- They absorb food across membranes
- They move using pseudopodia (false feet). They are like cytoplasm’s extensions and they experience ameboid movement.
- They ingest food through surrounding and engulfing food by a process known as endocytosis. This happens by creating a food vacuole.
- They reproduce binary fission or mitosis
- They have a contractile vacuole that removes excess water.
Examples of sarcodines are Ameba, Heliozoans and Foraminferans.
They can cause amebic dysentery in human beings. This will manifest through stomach upsets and diarrhea if one drinks contaminated water (Margulis & Schwartz).
A good example here is Paramecium
- They move using cilia
- Has two nuclei namely: micronucleus and macronucleus
- They gather food through the mouth using mouth pores. Food is then moved into a gullet, and then forms a food vacuole. The anal pore is used for waste removal
- Excess water is removed by contractile vacuole
- Reproduces sexually (conjugation) or asexually (binary fission).
- They exhibit avoidance behavior
- Their pellicle (outer membrane) is rigid their paramecia have the same shape as shoes.
- They don’t move on their own
- They cause malaria and infect blood and the liver.
Some protozoa live symbiotically within other organisms like Trichonympha that lives in intestines of termites. Many live in seas and lakes. They are eaten by tiny animals and in turn serve sea food for lager sea animals.
Plant like Prorists (Algae)
Algae perform photosynthesis and are classified into seven major phyla depending on various cellular characteristics. The initial four phyla are made up of unicellular organisms. They are: Euglenophytes, Chryophytes, Diatoms, and Dianoflagellates. The last three phyla are made up of multicellular organisms. They include: Red, Green and Brown algae (Margulis & Schwartz, 1998).
Unicellular plant like prorists
- They have two flagella and have no cell wall
- They are found in ponds and lakes
- They contain reddish pigment referred to as eyespot that helps them find sunlight for photosynthesis.
- Incase of no sunlight, they live like heterotrophs
- Are among the most beautiful and abundant organisms on earth.
- They produce thin and delicate cell walls that are rich in silicon
- Most of them are luminescent, giving off light.
Role of unicellular Algae
The silicon produced by diatoms is the main component of glass. They also from part of phytoplankton found near surface of ocean, that carries out photosynthesis and hence provision of direct source of nutrition to marine organisms. Algal blooms play an important role in sewage and other waste waters recycling. However, due to excessive waste, these prorists grow into massive masses called blooms. They deplete water of oxygen making cells to die on a large scale that disrupts aquatic systems’ equilibrium (Margulis & Schwartz, 1998).
Multicellular plant like prorists
- Share most characteristics with plants like their cell wall composition and photosynthetic pigments.
- They contain cellulose in cell walls.
- They contain chlorophyll a and b and they additionally store food inform of starch in the same manner like land plants
- They are found in both fresh and salt water and even on land in moist areas.
Uses of Algae
Margulis & Schwartz (1998) affirm that they are major sources of food for ocean life forms. Secondly, they produce most of the earth’s oxygen through their photosynthesis process. Chemicals that are produced by algae have medicinal value as they treat stomach ulcers if when utilized in foods rich in iron and vitamin C.