THE TOOLS AND EQUIPMENTS USED IN MICROBIOLOGY

LAMINAR AIR FLOW

PRINCIPLE

It is an apparatus consisting of an aerator in the rear of the chamber which can produce air flow with uniform velocity along parallel flow lines. There is a special high efficiency particle air filter (HEPA) filter system capable of removing small particles up to 0.3 nm.

WORKING

1. In front of the blower, there is a mechanism by which the air blown by the blower produces air velocity along parallel flow lines.
2. One fluorescent tube and the other UV tube are mounted inside the camera. Due to the uniform speed and parallel flow of the air flow, fluids, plates, inclined preparations, strips, etc. are poured. without any contamination.
3. Initially, the dust particles are removed from the laminar flow surface with the help of a soft cloth containing alcohol. Turn on the UV light for a period of 30 minutes to kill germs, if present in the work area.
4. All work related to casting, plating, scratching, etc. It should be done in the area of ​​the burner flame or spirit lamp.

PRECAUTIONS: -

Take off your shoes before entering to use the appliance. Wash your hands with detergent or soap. Do not speak inside the chamber during the transfer of the microbial culture, in the event that the chances of contamination are greater, orally, sneezing or air.

Source:- Researchgate

 

AUTOCLAVE

PRINCIPLE: -

The killing action of heat on the organisms can be done by using increase in the stream in a closed system. The water molecules become aggregated resulting in increase in their penetration. The water boils at 1000C and the steam accumulates in a closed container resulting in increase in pressure.

WORKING

1. The autoclave is usually of pressure cooker type made up of gun metal sheets which is supported in an iron case.
2. It is closed by swing door which is fastened by radical bolts tightly.
3. In microbiology laboratory, system jacketed horizontal type autoclave is necessary.
4. The steam passes from below at the base. The side walls are heated by the steam jacket. It has a provision to record the pressure.
5. There is a possibility to regulate the pressure using pressure meter. It consists of safety valve that guards against the accidents. It is based on moist heat that used sterilisation.
6. The autoclave is usually operated at 15 lb/inch2 steam pressure for 30min. As demonstrated in the table. The temperature for 30min. is enough to kill all the spores and cells of micro organisms.

PRECAUTIONS

The level of water should be checked before operating. The air should be completely evacuated and the steam must have access to the materials to be sterilised. The cotton or glass beads must be sterilised in a glass container closed with foil. The heat sensitiser substances should not be sterilised by autoclaving.

Source:- pharmawiki

INCUBATOR

PRINCIPLE:

Consists of copper/steel chamber, around which warm water or air is circulated by electric current or by means of small gas flame.

WORKING

1. The temperature of incubator is kept constant due to its control by using thermostat.
2. It is made up of double walled chamber adjusted to a desired temperature. It is done by using an external knob controlling the thermostat system. The gap between two walls is insulated to check heat conduction. A thermometer is inserted from the top for recording the temperature.
3. It is operated to allow the microbial growth on a suitable medium under proper temperature. The temperature variation should not be more then 1°.
4. If a lower temperature than the room is required, the water is circulated around the chamber to pass through an ice chest.

PRECAUTIONS

The door of the incubator should be opened only when necessary. If the tubes are to be incubated for a long time or at a higher temperature, the medium may become too dry due to excessive evaporation. In such cases cotton plug should be pushed inside the neck of the tube. The tube should be covered by a rubber cap so as to cover the plug.

Source:- Slideshare

LABORATORY OVEN

PRINCIPLE

Generally used for the sterilization of glass objects, metal devices and other items that are autoclaved. Dry heat sterilization is used for this. Ovens based on its principle. Although sterilization can be done in an autoclave, glassware requires dry heat rather than wet heat. It kills microbes by oxidizing their chemical components. It is less effective than wet heat.

WORKING

1. The ovens generally consist of a double-walled chamber, the space between two walls is insulated. It is heated from below by electric current and the heating elements are arranged in several parts to uniformly heat the internal chamber.
2. There is a built-in thermostat when needed, it helps regulate the temperature. The calibration knob sets the desired temperature.
3. For sterilization, the holding time depends on the temperature. For a temperature of 160 ° C, the holding time should be 1 hour and at 180 ° C 30 minutes.

PRECAUTIONS

The glasses must be cleaned and dried before storing them inside the chamber, otherwise they may break. At the end of the retention time, the glassware must not be removed immediately, the temperature should drop so that the cold air from the external environment cannot damage or break the glassware. The air inside the oven must circulate through a fan to ensure that all parts are kept at the required temperature, the items must be positioned correctly so as not to obstruct the air flow.

Source:- Pharmawiki

THE pH METER

PRINCIPLE

In 1909, Sorenson used the term pH to indicate the concentration of hydrogen ions in the solution.

pH = -log10 (H +) = 7

pH is the degree of acidity and alkalinity of a solution on a scale from 1 to 14. The acid pH is a proton donor and the base is a basic acceptor (acid = base + H +), i.e. the acid is it dissociates and produces H +.

WORKING

1. The pH is measured using a pH meter which is an instrument calibrated on a series of buffers of known pH values.
2. A standard pH meter has two electrodes, a glass electrode and the second mercury chloride (calomel) or silver-silver chloride reference electrode. The reference electrode emerges in a saturated KCl solution.
3. A normal pH meter consists of a glass electrode consisting of a thin glass membrane which is selectively permeable to H +.
4. Therefore, the fixing of the electrode is to form a conductive bridge between the metal element and the sample solution in which two electrodes are positioned.

PRECAUTIONS

It must be handled with care so that the electrode does not break. The electrodes must always be kept in distilled water so that they do not work.

Source:- Alibaba

Reference

Harley, J. P., & John, H. (2008). Microbiology Lab Manual. McGraw-Hill Science.

Seeley Jr, H. W., & VanDemark, P. J. (1962). Microbes in action. A laboratory manual of microbiology. Microbes in action. A laboratory manual of microbiology.

Hurst, C. J., Crawford, R. L., Garland, J. L., & Lipson, D. A. (Eds.). (2007). Manual of environmental microbiology. American Society for Microbiology Press.

Cappuccino, J. G., & Sherman, N. (2005). Microbiology: a laboratory manual (p. 507). San Francisco: Pearson/Benjamin Cummings.