Final answer:
The use of ribosomal RNA analysis has become essential in classifying bacteria alongside methods such as Gram stain reaction and the examination of physical and structural characteristics.
Step-by-step explanation:
Scientists use various methods to classify bacteria and determine taxonomic groupings, with Bergey's Manual as a definitive reference. In initial stages, the Gram stain reaction is often the first criterion, which is followed by the examination of physical and structural characteristics such as cell size and arrangement. However, to gain more detailed and precise classifications, scientists rely heavily on biochemical assays to create a biochemical profile and ribosomal RNA analysis, especially for bacteria that appear morphologically similar. While Bergey's Manual uses the nature of the bacterial cell wall for primary categorization, DNA and rRNA sequencing are integral in identifying bacterial species and for systematic classification of new species.
In summary, while physical characteristics like cell wall properties, staining reactions, and morphology are important, the use of ribosomal RNA analysis has become a key tool for the modern classification and identification of bacteria.