* We've only discovered a small fraction: Scientists have only been able to culture and study a tiny percentage of bacteria in the environment. Most bacteria can't be grown in a lab, making them difficult to identify and study.
* Definitions are tricky: The definition of a bacterial "species" is debated. Traditional methods based on morphology (shape) and metabolic traits are being challenged by genetic analysis, which is revealing surprising diversity within seemingly identical species.
* Constant evolution: Bacteria are constantly evolving and adapting. New species are emerging all the time, while others are disappearing.
Estimates:
* Current estimates suggest there are millions of bacterial species on Earth.
* Some scientists believe there could be billions.
So, while we can't give a definitive number, we know there is a staggering diversity of bacteria out there. This diversity is crucial for the health of our planet and ourselves.
