Basics of Bacteriology

Bacteriology is derived from the root word bacteria and the Greek word, "logos" (study); simply stated as the study of bacteria. It is not as simple as that though, because this field of science also includes the study of the structure, specific functions and the corresponding actions of the bacteria on living organisms. The study of bacteria is a very interesting field of microbiology; but what are bacteria?

Bacteria are microorganisms that have the following characteristics:

1.
They are subdivided into 3 phenotypic categories namely:

1.1.
Gram-positive with cell walls. These are bacteria that are colored violet when stained because they absorb the initial stain.

1.2
Gram-negative with cell walls. These are bacteria that do not absorb the initial stain but the secondary stain instead and are colored pink.

1.3. Without cell walls. These are the bacteria that do not have protective out covering.

2.
Bacteria could also be classified through their cell morphology. They have 3 basic types:

2.1.
Spherical or round which are called cocci.

They usually stain gram-positive (take up the initial stain- crystal violet) and may occur in pairs (diplococci), or in chains (streptococci), or in clusters (staphylococci). There are exceptions to the rule with regards to the staining methods; like the Neisseria species, which are pink because they are gram-negative.

2.2.
Rectangular or rod-shaped which are called bacilli

They may occur singly, in pairs or in chains. They usually stain gram-negative (take up the counter stain safranin). There are exceptions to the rule too; one is Bacillus anthracis which is gram positive.

Short rounded rods are called coccobacilli. The family Enterobacteriaceae is examples of bacilli

2.3.
Spiral or curved shaped which are called spirilla. Examples of these are the Vibrio species. The spiral shaped are called spirochetes. One example is the causative agent of syphilis, Treponema pallidum, which is coiled tightly.

2.4.
There are certain species which could not be classified through grams staining because their waxy cell wall could not take up the gram stain, but only through the Acid fast stain (Uses carbol fuchsin and heat). Examples of these are the Mycobacterium species like Mycobacterium tuberculosis, the causative agent of tuberculosis.

3.
Bacteria could also be classified by their motility:

3.1.
Motile they could move through the use of flagella
( whiplike projections), pseudopods ( blunt projections), cilia ( hairlike projections)

3.2.
Non-motile they stay immobile and stationary because they lack the means of locomotion.

4.
Bacteria could be classified according to their pathogenicity

4.1.
Pathogenic these are

diseases causing because they have capsules, pili and enterotoxins, like Bacillus anthracis- causes anthrax

Clostridium botulinum causes botulism, and many others.

4.2.
Non-pathogenic these do not cause any disease. Examples are

Lactobacillus in the stomach, Staphylococcus in the skin, etc.

5.
Bacteria could be classified according to their oxygen requirement into:

5.1.
Obligate aerobe those that need oxygen to survive.

5.2.
Microaerophile those that could survive with little amount of oxygen.

5.3.
Facultative anaerobe those that could survive in non-oxygenated and oxygenated environment.

5.4.
Aerotolerant anaerobe those that are facultative anaerobe but could grow in the presence of oxygen.

5.5.
Obligate anaerobe those that are incapable of surviving in the presence of oxygen.

5.6.
Capnophiles they need elevated concentrations of carbon dioxide.

6.
They could be cultured in agar media to form colonies (clumps of bacteria) and stained through differential stains and examined for their morphological characteristics. This will help clinicians identify the bacteria, and consequently the disease present in the patient.

7.
Culture and sensitivity could also be performed to determine what drug could cure the disease.
The bacteria are made to multiply by culturing them, and then are tested against antibiotics, whether they are resistant or sensitive to the drugs.

8.
All bacteria also need carbon, nitrogen, hydrogen, oxygen, sulfur and phosphorus and also some of the ions like potassium, calcium, etc. in order to survive.

Bacteriology is a dynamic and fast growing science. Up to this day, scientists are still discovering other bacteria which could be significant to man. As long as the world continues to exist so would these bacteria, whether pathogenic or non-pathogenic, also continue to proliferate.