The phylum Bacteroidetes
is composed of three large groups of bacteria with the best-known category being Bacteroidaceae
. This family of gram-negative bacteria is found primarily in the intestinal tracts and mucous membranes of warm-blooded animals and is sometimes considered pathogenic.
are the genus Bacteroides and Prevotella
. The latter genus was originally classified within the former (i.e. Bacteroides), but since the 1990’s it has been classified in a separate genus. Bacteroides and Prevotella
are gram-negative, anaerobic, rod-shaped bacteria that inhabitant of the oral, respiratory, intestinal, and urogenital cavities of humans, animals, and insects. They are sometimes pathogenic.
are considered for several reasons an interesting alternative to more traditional indicator organisms such as E. coli and Enterococci
. Since they are strict anaerobes, they are indicative of recent fecal contamination
when found in water systems. This is a particularly strong reference point when trying to determine recent outbreaks in fecal pollution. They are also more abundant in feces of warm-blooded animals than E. coli and Enterococci
. Furthermore, these latter two organisms are facultative anaerobes and as such they can be problematic for monitoring since it has been shown that they are able to proliferate in soil, sand and sediments.
The Human Bacteroidetes ID
™ service is designed around the principle that fecal Bacteroidetes
are found in large quantities in feces of warm-blooded animals. Furthermore, certain categories of Bacteroidetes
have been shown to be predominately found in humans. Within these Bacteroidetes
, certain strains of the Bacteroides and Prevotella
genus have been found to be specific to humans. As such, these bacterial strains can be used as indicators of human fecal contamination
An advantage of the Human Bacteroidetes ID
™ service is that the entire portion of water sampled is filtered for Bacteroidetes
. As such, this method avoids the randomness effect of culturing and selecting bacterial isolates. This is an advantage for highly contaminated water systems with potential multiple sources of fecal contamination
Accuracy of the results is possible because the method uses quantitative PCR (qPCR) DNA technology. qPCR allows quantities of DNA to be amplified into a large number of small copies of DNA sequences. This is accomplished with small pieces of DNA called primers that are complementary and specific to the Bacteroidetes
Through a heating process called thermal cycling, the double stranded DNA is denatured and inserted with complementary primers to create exact copies of the DNA fragment desired. This process is repeated rapidly many times ensuring an exponential progression in the number of copied DNA. If the primers are successful in finding a site on the DNA fragment that is specific to the genome to be studied, then billions of copies of the DNA fragment will be available and detected in real-time. The accumulation of DNA product is plotted as an amplification curve. The absence of an amplification curve indicates that the Bacteroidetes
Human gene biomarker is not present. To strengthen the validity of the results, the Human Bacteroidetes ID
™ service should be combined with other DNA analytical services such as the Human Enterococcus ID
™ and Human Urine Virus ID