General Characteristics of Microorganisms, Biology tutorial


Microorganisms or simply microbes are exactly microscopic organisms (that is, not visible with the naked eye), Microorganisms are frequently described by using single-celled or unicellular organisms; though, some unicellular protists are visible to the bare eye and some multicellular species are microscopic. Micro-organisms are the most abundant organisms in any ecosystem. There are around 159,000 known species; however this is thought to be less than 5 percent of the total in existence. There is huge genetic diversity among micro-organisms, which is not astounding as they start evolving over a billion years before land plants. Microorganisms are widespread in nature and are helpful to life; however a few can cause serious harm. They can be categorized into five main types: bacteria, fungi, protozoa, algae and viruses.

Characteristics and functions of Microorganisms:

1) Microorganisms utilize fermentation reactions (that is, protein) to carry out complicated synthesis beneath normal pressure and temperature. Thus equipment based on the microorganism reactions is simpler than equipment utilizing physico-chemical reactions and methods, and makes it probable for complicated reactions to be driven proficiently.

2) Among the living organisms, microorganisms are differentiated or characterized by quick proliferation rate and are capable of rapidly transforming substances. (That is, the volume of oxygen utilized by microorganisms is millions of times that needed by humans, on a per-unit-weight basis.) .

3) Microorganism's procedure materials contained in waste-water, which can't be decomposed via other means.

4) Microorganisms control themselves so as to make an organic layer appropriate for processing the liquid waste. (That is, Self-regulating function).

5) Microorganism reactions are harmless and safe, and cause no hazard of secondary pollution.


Bacteria are generally unicellular organisms. The cells are illustrated as prokaryotic as they are deficient in a nucleus. They exist in four main shapes: bacillus (that is, rod shape), coccus (that is, spherical shape), spirilla (that is, spiral shape) and vibrio (that is, curved shape). Most of the bacteria encompass a peptidoglycan cell wall; they split by binary fission; and they might have flagella for the motility. The difference in their cell wall structure is a main feature utilized in categorizing such organisms.

According to the manner their cell wall structure stains, bacteria can be categorized as either Gram-positive or Gram-negative if employing the Gram staining. Bacteria can be further categorized based on their response to gaseous oxygen to the given groups: aerobic (that is, living in the presence of oxygen), anaerobic (that is, living with no oxygen) and facultative anaerobes (that is, can live in both the environments).

According to the manner they get energy, bacteria are categorized as autotrophs and heterotrophs. Autotrophs prepare their own food by utilizing the energy of sunlight or chemical reactions, in which case they are termed as chemoautotrophs. Heterotrophs get their energy through consuming other organisms. Bacteria which utilize decaying life forms as a source of energy are termed as saprophytes.


Fungi (such as mushroom, molds and yeasts) are eukaryotic cells (that is, having a true nucleus). Most of the fungi are multicellular and their cell wall is comprised of chitin. They get nutrients by absorbing organic material from their environment (that is, decomposers), via symbiotic relationships with plants (that is, symbionts), or harmful relationships by a host (that is, parasites). They make characteristic filamentous tubes termed as hyphae which aid in absorbing material. The collection of hyphae is termed as mycelium. Fungi reproduce through releasing spores.

Fungi are categorized on the basis of their life-cycles, the presence or structure of their fruiting body and the arrangement and kind of spores (that is, reproductive or distributional cells) they produce.

The three main groups of fungi are:

a) Multicellular filamentous moulds.

b) Macroscopic filamentous fungi which form big fruiting bodies. At times the group is termed to as mushrooms; however the mushroom is just the portion of the fungus we notice above ground which is as well recognized as the fruiting body.

c) Single celled microscopic yeasts.


However viruses are not considered as living organisms, they are at times categorized as microorganisms. Viruses are much smaller than the general microbes. They are made up of a DNA molecule covered by a protein shell termed as a capsid. Retroviruses are building up of an RNA molecule covered by a capsid. Capsid can take numerous shapes. Viruses can't reproduce outside the host cell; however they can't be termed as parasites either. Scientists still argue nowadays about whether viruses are true living forms as they are not cells and they can't metabolize on their own.

Viruses can infest eukaryotic and prokaryotic cells, often causing diseases in the organisms. A virus which infects bacteria is termed as a bacteriophage.


Algae, as well termed as Cyanobacteria or blue-green algae, are unicellular or multicellular eukaryotes which get nourishment through photosynthesis. They live in damp soil, water and rocks and generate oxygen and carbohydrates employed by other organisms. It is assumed that Cyanobacteria are the origins of the green land plants.

Most of the algae live in fresh or sea-water where they can either be free-floating (that is, planktonic) or joined to the bottom. A few algae can grow on rocks, soil or vegetation as long as there is adequate moisture. Several algae form much close partnerships with fungi to form lichens.

Each and every algae contain a pigment termed as chlorophyll a (other kinds of chlorophyll like b, c or d might too be present) and they prepare their own food by the process of photosynthesis. The chlorophyll is contained in the chloroplasts and provides most algae their green appearance. Though some of the algae appear yellow, brown or red because in addition to chlorophylls they have other accessory pigments which camouflage the green color.


Protozoa are basically unicellular aerobic eukaryotes. They encompass a nucleus, complex organelles and accomplish nourishment through absorption or ingestion via specialized structures. They make up the biggest group of organisms in the world in terms of numbers, biomass and diversity. Their cell walls are building up of cellulose. Protozoa have been traditionally classified based on their mode of locomotion: flagellates generate their own food and employ their whip-like structure to propel forward, ciliates encompass tiny hair which beat to produce movement, amoeboid include false feet or pseudopodia employed for feeding and locomotion and sporozoans are non-motile. They as well encompass different means of nutrition that groups them as heterotrophs or autotrophs.

A few of them are parasitic that means they live in other plants and animals comprising humans, where they cause disease. Plasmodium, for illustration, causes malaria. They are motile and can move through:

a) Cilia: Tiny hair like structures which cover the exterior of the microbe. They beat in a regular nonstop pattern such as flexible oars.

b) Flagella: Long thread-like structures which extend from the cell surface. The flagella move in a whip-like motion which generates waves that propel the microbe around.

c) Amoeboid movement: the organism moves by sending out the pseudopodia, temporary protrusions which fill with cytoplasm which flows from the body of the cell.

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