A researcher investigates a blood disease carried by birds. She isolates an organism from the blood of an infected bird. She finds that the organism is unicellular and has a nucleus, a cell wall, and the ability to produce spores. What kingdom does the organism belong to .

Bacteria

Explanation:

Bacterial are prokarotes, that inhabit virtually all habitats..Although some may be pathogenic, ,most bacteria are beneficial. They live in mutual relationship with their living hosts.where they help  most in catabolic  reactions especially in digestion of  food and  in nutrient cycle.

They lack membrane bound organelles,they have cell wall  made up of peptidoglycan, their nucleus is not bounded with double membrane like Eukaryotes.They  vary  in shapes, most are spherical in shape, with the shape determined by the cell wall and the cytoskeleton  in the cystosol.