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.

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.

Fungi (Eukaryote)

Fungi are eukaryotic organisms that produce long filaments called hyphae, which form a mass called mycellium. Chitin is a characteristic component of the cell wall of hyphae. In most fungi, the hyphae are septate and contain crosswalls that divide the filament into separate cells containing one nucleus each. In some others,the hyphae are nonseptate and contain several nuclei. They are called coenocytic hyphae.

Unusual Types of Bacteria (Part 3)

. Actinomycetes

Actinomycetes are gram-positive filamentous bacteria characterized by mycelial growth (i.e., branching filaments), which is analogous to fungal growth. However, the diameter of the filaments is similar in size to bacteria (approximately 1 mm). Most actinomycetes are strict aerobes, but a few of them require anaerobic conditions. Most of these microorganisms produce spores, and their taxonomy is based on these reproductive structures (e.g., single spores in Micromonospora or chains of spores in Streptomyces). They are commonly found in water, wastewater treatment plants, and soils (with preference for neutral and alkaline soils). Some of them (e.g., Streptomyces) produce a