Thursday, April 3, 2014

Spore stain

Some Gram-positive bacteria produce endospores which are highly resistant to heating and a variety of chemicals. These spores are found in the genera Bacillus and Clostridium. The spores are difficult to stain using normal techniques, but it is possible to drive the stain into them using heat. Once the stain has been taken up by the spores, it is extremely difficult to decolourise them, although the vegetative portion of the cell can be decolourised easily. Several versions of the spore stain are used.

Gram Stain

This is the most important stain in bacteriology and is so central to identification that it should be practised until the operator is fully competent. A number of different variations are found, and the laboratory should standardise on one method.

Saturday, March 29, 2014

A General Model for Biofilm Development

Biofilm formation is a developmental process in which bacteria undergo a regulated lifestyle switch from a nomadic unicellular state to a sedentary multicellular state where subsequent growth results in structured communities and cellular differentiation. Results of prior work by many groups allow the construction of a hypothetical developmental model for biofilm formation that can be generalized for many different bacterial species. This model can be adjusted to fit either of two general modes of unicellular lifestyle: nonmotile and motile.

Thursday, March 27, 2014

Transport of an Infectious Agent

Transmission involves the transport of an infectious agent from the reservoir to the host. It is the most important link in the chain of infection. Pathogens can be transmitted from the reservoir to a susceptible host by various routes (Sobsey and Olson, 1983).

a. Person-to-Person Transmission

The most common route of transmission of infectious agents is from person to person. The best examples of direct contact transmission are the sexually transmitted diseases such as syphilis, gonorrhea, herpes, or acquired immunodeficiency syndrome (AIDS).

Determination of Cell Biochemicals

Microbial biomass can also be measured by determination of specific cell biochemical constituents such as ATP, DNA, RNA, proteins, phospholipids, bacterial cell wall components, or photosynthetic pigments (Sutton, 2002).

a.        ATP
Adenosine triphosphate has often been used to determine live microbial biomass in environmental samples, using a ratio of C/ATP = 250 for aquatic samples. However, the ATP content of cells varies with the growth rate and metabolic state of microorganisms and nutrient limitation. A better measure is the total adenylate pool AT (AT = ATP + ADP + AMP) because it does not change greatly with changes in metabolic activities of the microorganisms. The adenylate energy charge (EC) ratio provides information on growth potential of naturally occurring microbial populations.