Final answer:
Granulicatella spp. and Abiotrophia spp. are fastidious bacteria that require the addition of vitamins, specifically vitamin B6 (pyridoxal), as a growth factor for optimal growth.
Step-by-step explanation:
Granulicatella spp. and Abiotrophia spp. require the addition of vitamins or other growth factors for optimal growth, as they are considered fastidious bacteria. These microorganisms are known to have specific nutritional requirements that cannot be met by basic microbiological media, which generally contains protein extracts, inorganic salts, and sometimes carbohydrates.
For their growth, specific nutrient supplements such as vitamins must be included in the culture medium. One commonly required additive for the culture of such bacteria is vitamin B6 (pyridoxal), which acts as a growth factor. This dependence is observed because these bacteria lack certain metabolic pathways necessary to synthesize these compounds on their own. Therefore, microbiological media must be fortified with the necessary nutrients to support their growth.