The first behavior that comes to mind into a changing microbial gut community is not properly cleaning and cooking meats, especially chicken. Consuming raw or uncooked poultry introduces campylobacteria as well as salmonella and other bacteria that will cause discomfort and other gastrointestinal issues. Breaking this habit is not difficult though, learning how to prepare chicken is quite simple. It is not recommended that chicken is washed with water because that actually increases the risk of bacterial infection. It is better to just directly season it and cook. A cooking thermometer should be bought to directly test the temperature and make sure that it has an internal temperature of 165 degrees Fahrenheit. Besides just keeping foods clean it is just as important to keep hands and body clean as well. Washing hands after touching anything directly outside your home is essential to not introducing new potentially dangerous microbial species into your gut. If hands are kept dirty, who knows how much bacteria has accumulated over the day that is goin directly into the stomach if hands are not washed before consuming food. For young children it may be beneficial in developing their immune system to let them play on the floor and get dirty and sick as kids so that when they grow up their immune system will be stronger, but the older someone gets the more dangerous it is for them to introduce new species. Controlling the gut microbial community with prebiotics and probiotics can be helpful in ensuring the beneficial communities are able to grow. Faecal microbial transplantation is also a common way of replenishing GI micro bacteria and especially in circumstances where other treatment does not work.