To fight the virus
Not necessarily. Anaerobic bacteria play important roles in various ecosystems, such as breaking down organic matter in oxygen-deprived environments like wetlands. However, some anaerobic bacteria can also cause infections in humans if they enter the body through wounds or other means.
Facultative anaerobic bacteria can switch between using aerobic and anaerobic metabolism depending on oxygen availability. Obligate anaerobic bacteria cannot survive in the presence of oxygen and rely only on anaerobic metabolism, while obligate aerobic bacteria require oxygen for survival and use aerobic metabolism exclusively.
Aerobic bacteria uses oxygen for cellular respiration and anaerobic bacteria doesn't require oxygen to survive. ˇ_ˇ 
Some methanogenic bacteria (which are anaerobic) do have flagella. You can read more in the related link
Anaerobic media is a type of culture media used to grow microorganisms that do not require oxygen to survive. It creates an oxygen-free environment, usually by using an oxygen scavenger, to support the growth of anaerobic bacteria. Anaerobic media is important for studying and isolating anaerobic organisms in laboratory settings.
Bacteria that do not require aerobic respiration are known as anaerobic bacteria. These bacteria can survive and grow in the absence of oxygen by using alternative electron acceptors in anaerobic pathways such as fermentation or anaerobic respiration. Examples of anaerobic bacteria include Clostridium and Methanogens.
Anaerobic bacteria or facultative anaerobic bacteria.
anaerobic
aerobic bacteria use oxygen based respiration, anaerobic bacteria use either nonoxygen based respiration (e.g. nitrogen, sulfur) or fermentation.
Not necessarily. Anaerobic bacteria play important roles in various ecosystems, such as breaking down organic matter in oxygen-deprived environments like wetlands. However, some anaerobic bacteria can also cause infections in humans if they enter the body through wounds or other means.
anaerobic.
used for growth anaerobic bacteria
Salmonella bacteria are anaerobic.
Aerobic bacteria uses oxygen for cellular respiration and anaerobic bacteria doesn't require oxygen to survive. ˇ_ˇ 
Anaerobic means without oxygen. Those are anaerobic bacteria.
Firstly, pathogenic is not the opposite of anaerobic. The vast majority of bacteria are non-pathogenic, but this doesn't mean they are anaerobic.
Anaerobic bacteria are bacteria that do not live or grow in the presence of oxygen. In humans, these bacteria are most commonly found in the gastrointestinal tract.