Some organisms serve as bridging species by adhering to multiple different species. Which term describes this?

• A. Keystone species
• B. Bridging species
• C. Pioneer species
• D. Mutualist

Answer: (B)

The idea being tested is the role of an organism that can attach to multiple different species and physically connect them within a community. Such bridging species act as connectors in a biofilm or ecological network, enabling interactions and the progression of the community by providing adhesion points across diverse partners. In dental plaque, for example, a bridging organism like Fusobacterium nucleatum can bind to early colonizers (such as Streptococcus species) and later, more diverse, late colonizers, helping to unify the biofilm as it develops. This bridging function is about linking different microbial groups through shared adherence, rather than dominating the ecosystem, starting colonization on a barren surface, or engaging in a mutualistic relationship with a single partner. Therefore, the term that best fits is bridging species.