Final answer:
W and DSM codes are identifiers for bacterial strains or types in scientific databases, with DSM being a specific code for microbial strains in the German Collection of Microorganisms. The terms gram-positive and gram-negative reflect differences in bacterial cell wall structure, assisting in bacterial classification. The E value in sequence alignment signifies the statistical significance of a match, where lower values indicate more significant similarities.
Step-by-step explanation:
The 'W' and 'DSM' codes provided refer to specific identifiers for bacterial strains or types in scientific literature and databases. In the context of the provided excerpts, 'W' seemingly refers to the name 'Waksman' which could be associated with a specific strain of bacteria, or to a classification like in the case of 'walking pneumonia' caused by Mycoplasma pneumoniae. On the other hand, 'DSM' refers to the Deutsche Sammlung von Mikroorganismen (German Collection of Microorganisms) code, which is a unique identifier for microbial strains held in a microbial 'type culture collection' used worldwide for scientific research, including the study of bacteria such as 'Pseudomonas stutzeri DSM 4166'.
Bacteria can be classified as gram-positive or gram-negative based on their cell wall composition. Gram-positive bacteria have a thick peptidoglycan layer which retains the crystal violet stain used in the Gram-staining procedure. In contrast, gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane containing lipopolysaccharides (LPS) which do not retain the crystal violet stain but can be stained by the counterstain safranin. Therefore, whether a bacterium is gram-positive or gram-negative reveals significant details about the structure of its cell wall.
The E value in the context of sequence alignment refers to the expected number of hits one can expect to see by chance when searching a database of a particular size. It helps in assessing the statistical significance of an observed sequence similarity; a low E value indicates a more significant match.