Protozoa vs Bacteria
Out of all the present biomass of the Earth, the vast majority is the microorganisms. The importance of these microorganisms would never be imaginable, given their existence could never be compared with other living beings. Therefore, it would be important to know some understood characteristics of them. The modern biological classification describes all the living beings inside three domains (Bacteria, Archaea, and Eukaryotes), which are placed at the highest level of the hierarchy above the well-known kingdom level. Both protozoa and bacteria are microscopic, yet they exhibit very important differences between them, mainly in taxonomic diversity, body size, and other biological aspects.
Protozoa
Protozoa is one of the main groups of the Kingdom: Protista, which consists of unicellular eukaryotic organisms of a diverse array. Protozoans include organisms related to both animals and plants. Therefore, they have been termed as either phylum or division. However, protozoa are, sometimes, considered as an out-of-date taxonomical clade as DNA analysis information is not available for most them. Nonetheless, four main Subphyla have been described under protozoans based on the mode of locomotion known as Ciliates (Ciliophora), Flagellates (Sarcomastigophora), Amoeboids (Cnidosphora), and Sporozoans (Sporozoa).
Majority of protozoans are motile; ciliates, flagellates, and amoeboids move using their cilia, flagella, or pseudopodia respectively. A significant portion of the protozoans being heterotrophic, they move energy into their consumers from bacteria and algal production. Some members such as Euglena are autotrophs because they can produce their own food from photosynthesis. Their cell sizes range from 10 through 52 micrometres, and they are always unicellular organisms.
Protozoans can exist almost everywhere including water, soil, and inside animals or plants. Some of the protozoans such as Plasmodium, Entamoeba, Giadia, etc. are pathogenic for humans. There are some protozoans with symbiotic relationships with large organisms. Protozoans being a highly diversified group of microorganisms, more than 36,000 species have been identified.
Bacteria
Bacteria could be described as the most diversified group among all the living beings, with about 107 or 109 of species according to some of the highly respected estimations. However, the total number of identified species count makes only slightly above 9300 species collectively with Archaea. It would be interesting to know that there are more than five nonillions (5 x 1030) bacteria living on the Earth. The fact that bacteria possess the most successful existence on Earth could be satisfied with those figures. In addition, it would be important to state that the number of bacteria cells in a human body is ten times more than the number of human cells. Their successful existence could be described using their wide range of habitats, in addition to soil and water, such as acidic hot springs, very deep Earth crust, and radioactive waste. Hence, they can be labelled as extremophiles.
Bacteria being parts of many symbioses with multicellular animals, especially on the skin and gut, they pose very important ecological significance. Bacteria possess various morphologies including coccus, bacillus, coccobacillus, and other shapes. They live either as colonies or singularly. The colonies could be in the forms of either unicellular or multicellular chains. Their cell sizes vary from 0.5 through 5 micrometres. However, there are very few members with sizes reaching up to 500 micrometres those could be spotted by the naked eye. This highly diverse and abundant group of organisms have a big say in the world.
What is the difference between Protozoa and Bacteria?
• Protozoa is a sub group of Kingdom: Protista, which comes under the Eukaryotes domain, whereas bacteria could be described as an entire taxonomical domain.
• Number of identified bacteria species is lower than that of protozoa. However, the actual number of bacteria species is vastly greater than the number of protozoa species.
• Bacteria are prokaryotes while protozoans are eukaryotes.
• Incidence of bacteria on Earth is greatly higher than protozoa.
• Bacteria are extremophiles but not protozoans.
• The body sizes of protozoans are usually higher than the bacteria.