The PhenePlate System
Typing of bacteria means identification of strains below the species level. Typing is required when the aim is to follow the spread of bacterial strains, such as in epidemiological or nosocomial investigations, and is very useful in studies of the diversity or stability of bacterial populations in ecological investigations.
Typing methods can be based on different characteristics of the bacteria. In genotyping, the composition of bacterial DNA/RNA is studied by molecular methods. Chemotyping involves chemical characterization of contents of the bacterial cell, and phenotyping means studying the appearance or the reactions of the bacterial cell.
Since both the chemotype and the phenotype of a bacterial cell depend on the expression of its DNA, they are both indirect measures of the genotype of the cell.
Ask instead: Why do we normally use photographic portraits in order to recognize humans instead of their DNA-fingerprints? – It is of course because the photographic portrait of the human (the phenotype) is so simple, rapid and cheap, and, if it is properly done, gives all the information that is required to recognise a particular individual. However, in some instances, the genotype may give additional information that can not be obtained in other ways, or may be needed to verify important findings. The same is applicable for bacteria: phenotyping is normally much simpler to use than genotyping, and often gives the required information, but in some cases phenotyping can not be performed, and in some cases genotyping is required in order to obtain information that the phenotype can not yield. So the answer is: use phenotyping when possible, and genotyping as its complement.
Biochemical fingerprinting means characterization of bacterial strains based on quantitative measurements of reaction products formed by the bacterial metabolism of several different substrates. It is based on the concept that bacterial isolates with identical genotypes, i.e. belonging to the same clone, share identical metabolic properties, whereas isolates with different genotypes also have differences in one ore more of the measured metabolic processes, and thus will show different activities in the reactions involved.
The PhenePlate (PhP) system – macro-arrays for fingerprinting of bacteria
The system is based on the evaluation of the kinetics of biochemical reactions, performed in preprepared micro plates. Each test has been carefully selected to give an optimal discriminatory power and reproducibility for the studied bacterial group.
The PhenePlate system is suitable for investigations involving large numbers of bacterial isolates
It can be used as a first screening method in order to select important isolates to be further studied by other methods. For ecological investigations, the components of whole bacterial populations may be characterized, and the diversity of each population, as well as the similarity between different populations, may be automatically calculated using the PhP software.
The PhenePlate system is suitable for many groups of metabolically active bacteria, e.g. most Enterobacteria, Aeromonads, Vibrios, Pseudomonas, Staphylococci, Enterococci etc.
The PhenePlate system is not:
the same as biotyping. In biotyping, reactions that differentiate between bacterial species, but that show homogeneous reactions within species are used. The PhenePlate system measures reactions that differentiate within species. In biotyping, reactions are read as + or -. The PhenePlate system uses information about the quantity of the reaction products formed, as well as about the kinetic of each reaction a species identification system (although reference data bases may easily be created, which may be used for species identification) suitable for metabolically inactive bacteria, or for bacterial groups showing low metabolic diversity