Bacteria that thrive in the absence of air are called anaerobic bacteria. They don't need oxygen to survive and in fact, oxygen can be toxic to some of them.

Here are some types of anaerobic bacteria:

* Obligate anaerobes: These bacteria cannot survive in the presence of oxygen. They use other molecules, such as sulfur or nitrate, as electron acceptors in their metabolism. Examples include:

* Clostridium botulinum: Causes botulism food poisoning.

* Bacteroides fragilis: Common inhabitant of the human gut.

* Clostridium difficile: Causes severe diarrhea.

* Facultative anaerobes: These bacteria can survive with or without oxygen. They prefer oxygen if it's available but can switch to anaerobic respiration if needed. Examples include:

* E. coli: Commonly found in the human gut.

* Staphylococcus aureus: Can cause skin infections and other illnesses.

* Salmonella: Causes food poisoning.

* Aerotolerant anaerobes: These bacteria don't use oxygen for metabolism but can tolerate its presence. Examples include:

* Streptococcus: Causes strep throat and other infections.

* Lactobacillus: Found in yogurt and other fermented foods.

Anaerobic bacteria are found in a variety of environments, including:

* The human gut: Many anaerobic bacteria live in our digestive system and are essential for our health.

* Soil and water: They play important roles in decomposition and nutrient cycling.

* Deep ocean trenches: These environments are devoid of oxygen.

* Dental plaque: They contribute to tooth decay.

It's important to note that not all anaerobic bacteria are harmful. In fact, many are essential for life on Earth. However, some can cause serious infections.