Bacteria, Biology tutorial


Bacteria are known as prokaryotic as they don't contain nuclear membrane. The nuclear material is spread on over cell that contain extremely few organelles. They are though extremely significant to living world due to their wide range of activities.

Features of Bacteria:

The features of Bacteria can be explained under given sub-heading- classification, size, structure and movement as all of these illustrate oddness of such organisms that is between smallest of all organisms of living things.

a) Size:

By utilizing light microscope, and its maximum possible magnification (100x) one can only view common shape of bacteria. Smallest bacteria are around 0005 micrometers m across. Largest may be up to .02 m long. We can determine bacteria in micrometers 1 micrometer is equivalent to 11000(one thousandth of a millimeter).

b) Classification:

There are more than 2000 bacterial species. In 3-kingdom categorization system they are categorized in kingdom protita. It can also be further categorized bacteria in terms of their shapes. Spherical are known as cocci; rod-shape are bacilli and spiral shaped are known as spirilla. Bacteria can also be explained with pre-fixes like - diplo - means two; staphylo - that means cluster; strepto that means chain, other factors are utilized to recognize bacteria. These comprise staining properties, size, conditions required for growth, and appearance of colony. The colony is large group of bacteria which arose from the single bacterium

c) Structure:

The bacteria have outermost chitinous cell wall that keeps it in form. Numbers of bacteria (mycoplasmas) that can vary their shape though don't contain cell wall at all. Others have cell walls which are less firm than others. A number of bacteria have the substance or coating on outside of cell wall with the specific boundary. Such coating is known as slime layer. These coats defend bacteria from viral infections, changes in environment and natural body defenses of the organisms that bacteria invade. Cell wall in some bacteria is strong and rigid as presence of murein that prevent cell from bursting when it absolves water with its minute pores. These pores permit passage of molecules. Sometimes bacteria are clustered by structures of the walls in Gram negative and Gram positive.

Every bacterium contains cell membrane on the inner surface. This surrounds cytoplasm of bacteria. Cell membrane in many organisms control substances which move in and out of organisms. So it is with bacteria. Cell membrane is site of most life tasks. Few bacteria form mesosomes that are in-folding of cell membrane. The nuclear area in bacteria have organisms DNA that is either spread within area, situated in the long single string or in small separate segments known as plasmids.

d) Surface Area/Volume Ratio:

As their small size, bacteria have the large surface/volume ratio that in the typical spherical bacterium can be stated as about 120,000, where as in the single cell animal such as amoeba it can be as low as 400. Surface/volume ratio is even smaller - the mere 0.3. This is the benefit for bacteria. Every life process can thus occur rather very fast with minimum hindrance by mass.

Growth and Reproduction:

The population of bacteria in the liquid medium is stated to as the culture. In lab, where growth situations of light intensity, temperature, and nutrients can be made perfect for bacteria, measurements of number of living bacteria usually reveals 4 phases of development, with respect to time. Originally, number of bacteria in population is low. Frequently bacteria are also adjusting to environment. This signifies lag stage of growth. Depending on health of bacteria, lag stage may be short or long. Last happens if bacteria are harmed or have been improved from deep-freeze storage.

Bacteria developing as colonies on the solid growth medium also show these development stages in different regions of the colony. For instance, bacteria buried in oldest part of colony are frequently in motionless or death stage, where as bacteria at margin of colony are in actively-dividing log stage of growth.

Feeding and Nutrition:

This is procedure by which organism acquires energy and fundamental material needed for growth. Organism can merely utilize 2 types of energy, either chemical or light. Those who utilize light phototrophs and those who utilize chemical sources are chemotrophs. Described by sources of the growth material, bacterial can also be clustered in autotrophs when source of carbon is in organic.

Photoautotrophic bacteria are similar to algae and plants as they perform photosynthesis and utilize carbon dioxide as carbon source. Blue-green bacteria dwell on top of fresh waters, and seas and fresh. They are also discovered as gelatinous mat-like development on shaded soils, rocks mud wood and some living organisms. Blue-green bacteria have chlorophylla such as plants in addition to features pigment known as phycocyanin. They produce oxygen in photosynthesis. Some blue-green bacteria such as Anabaena fix nitrogen of air of form ammonia from these protein compounds and amino acids can be synthesized. This is achieved by heterocysts that are cells which develop when there is lack of nitrogen. They export the nitrogenous compounds for other nutrient such as carbohydrates. Chemoheterotrophic bacteria get energy from chemical in the food that puts them in 3 fundamental groups:

Saprophytes: Those who feed on rotting and deed matter. They emit enzymes onto dead organic matter that get digested outside bacteria. Bacteria then absorb and incorporate soluble products of digestion. They are, together with fungi decomposers. They bring about decay and reprocessing of nutrients. Symbiosis (mutualism) explains relationship between 2 organisms which live together and derive advantages equally. Rhizobium is the bacteria living in roots of leguminous plants. Escherichia coli live in colon of man; possibly contributing vitamins B and K. whereas man provides it shelter. These are instance of symbiotics. Parasites, cause harm to the host on or where they survive. They are of dissimilar species from the host. When they are responsible to cause disease they are known as pathogens. Several bacterial are disease causing like pnenmococci, staphylococci etc.

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