The bacterial kingdom comprises a diverse set of microscopic organisms, ranging from single-celled to multicellular forms, which share common attributes but significantly diverge from the classifications of plants, animals, and fungi. These entities showcase a multitude of characteristics, such as unique cell structures and modes of reproduction. 

Bacteria play a pivotal role in ecosystems as they contribute to nutrient cycling, environmental balance, plant, animal and human health. Some bacteria are harnessed for industrial purposes, such as fermentation for food production or the synthesis of biofuels and enzymes. Additionally, they have applications in medicine, including the development of antibiotics and probiotics, further emphasizing their far-reaching impact.

Data retrieved from  The Catalogue of Life