Which subgroup of proteobacteria contains many species that are closely associated with eukaryotic hosts in mutualistic or parasitic relationships?

• A. Beta
• B. Gamma
• C. Delta
• D. Epsilon
• E. Alpha

Answer: (E)

Verified step by step guidance

1. Understand the context: Proteobacteria is a major phylum of Gram-negative bacteria, which includes a wide variety of pathogens. They are divided into several subgroups based on genetic and phenotypic characteristics.
2. Identify the key characteristic: The problem asks for the subgroup of proteobacteria that is closely associated with eukaryotic hosts, either in mutualistic or parasitic relationships.
3. Recall the characteristics of each subgroup: Alpha proteobacteria are known for their close associations with eukaryotic hosts. Many species within this subgroup form mutualistic relationships, such as Rhizobium, which fixes nitrogen in symbiosis with plants. Others, like Rickettsia, are parasitic.
4. Compare with other subgroups: Beta proteobacteria often include species involved in nitrogen fixation but are not primarily known for close associations with eukaryotic hosts. Gamma proteobacteria include many well-known pathogens like Escherichia coli but are not specifically noted for mutualistic relationships. Delta proteobacteria are known for their predatory behavior and complex life cycles, while Epsilon proteobacteria include some pathogens but are not primarily associated with mutualistic relationships.
5. Conclude based on characteristics: Given the information, Alpha proteobacteria is the subgroup most closely associated with eukaryotic hosts in mutualistic or parasitic relationships.