<P> There are four main species within streptococci: the mutans, salivarius, anginosus, and mitis groups . Streptococcus mutans make up a large majority of what affects our mouths . As a matter of fact, it is "the biggest culprit in tooth decay" as it promotes the production of acids and enzymes . The acids cause the collapse of enamel opening the door for the formation of decay . The enzymes "leach down the tooth and begin to dissolve the ligaments and bone that help to hold the teeth in your mouth ." By turning simple sugars and carbohydrates into acids and enzymes that dissolve tooth enamel, this bacteria can leave a person with lasting dental problems . According to Dr. Robert Gandola, a dentist, "A number of bacteria can cause decay (and many) are suspected in periodontal (gum) disease ." </P> <P> Oral bacteria work with our immune system to keep our bodies disease free by fighting disease - producing germs that try to come in through the mouth . For example, some of these bacteria produce organic acids that kill the organisms that cause intestinal problems . Without these good bacteria, our immune systems would be constantly bombarded by airborne and saliva - transferred germs . Bacteria are also needed to control the growth of fungus . "Balance between all the different bacteria and fungus are critical" or else the "fungus overgrows and takes over ." So, ironically, though bacteria have the potential to harm us, our mouth and the good bacteria in it are the body's first line of defense . These bacteria are transmitted to a human early in their childhood through their contact with their caretakers by kisses or food premastication . </P> <P> Numerous kinds of bacteria grow in the mouth . "They are competing for food and places to grow" and the many hard surfaces in the mouth provide an ideal place for bacteria and biofilms to grow and reproduce . Unlike most other places in or on the body, the mouth does not desquamate (shed). A tooth's distinct surface and stagnant nature makes it optimal for populations and growth of micro-organisms and bacteria, resulting in dental plaque . To grow and flourish in the mouth, biofilms go through four main stages of growth . First, bacteria must be deposited from saliva onto a surface where it can attach . Then the bacteria, or micro-organisms, grow and replicate . Since bacteria can grow exponentially in short periods of time, it can quickly and easily create biofilms . Third, the biofilm matures and accumulates more mass on the surface . Bacteria can continue to divide and grow by binary fission until nutrients begin to run out or their growth is inhibited . When this happens there is the final stage, the dispersal or detachment, causing the death of the bacteria . Some oral bacteria, Streptococcus gordonii for example, cannot last for long periods without nutrients, while other types of bacteria can survive for weeks . While in their prime, biofilms can cause major damage to a person's teeth and gums . Though damaging, biofilms can be partly removed by brushing and flossing and "some of it comes off with rinsing or eating ." We never really lose all of it because it is constantly being replenished by our own saliva . Bacteria can then reattach and start to grow and the cycle continues . Bacteria and its growth are two of the principal components of oral ecology . </P> <P> Though bacteria play a major role in oral ecology, another key part is saliva . Saliva keeps the ecosystem of the mouth in balance . It contains its own bacterial enzymes that are beneficial to our health . An example of these are lysozomes . These antibacterial agents in saliva kill bacteria in our mouths and protect from potentially dangerous diseases . In addition, saliva contains phosphate and calcium ions that help repair microscopic chinks made in the teeth by the bacteria's acid . The major organic constituents of saliva are proteins and glycoproteins . Proteins in saliva float around and influence the mouth's ecosystem in multiple ways . Some of the proteins provide nutrients for bacteria, while others cause bacteria to clump together so they are unable to stick to any surface and are washed away . The main function of saliva is to flush out all of the micro-organisms that could potentially threaten our health . The flow of saliva constantly bathes the mouth and detaches all micro-organisms that are not already firmly attached to a surface . This makes it difficult for bacteria to adhere to surfaces to even begin to form biofilms . Many harmful micro-organisms, therefore, are unable to attach quick enough to a surface before they are caught in saliva and swallowed . Although saliva does a lot to keep our bodies healthy, it cannot completely keep all bacteria from adhering to tooth, tongue or gum surfaces . </P>

Where does bacteria in the mouth come from