Bacteria can be floating free in water, not attaching to organic matter or roots. Can be motile, or mobile, which means actively moving in a directed fashion. Usually move in a straight line with abrupt reversals or turns. Can be attached to any surface: organic matter, roots, debris, clay, silt, sand, rock, pebble, etc. Produce glues to attach themselves to surfaces and glue together small particles into microaggregates. Aerobic bacteria produce glue materials that, on average, have a pH greater than 7 and maintain their environment at a pH above 7. Exactly how alkaline depends on the species of active, or growing, bacteria. (Please note that growing means active and performing their function; inactive cells do not contribute when they are not active.). Anaerobic bacteria produce organic acids in high amounts, thus maintaning conditions at a pH less than 7, often lower than pH 5. Bacterial cells contain the highest concentrations of nutrients as compared to any other living organism on the planet. Bacteria, therefore, immobilize and do not release nutrients of their own accord. As has been shown in many studies, bacteria immobilize nutrients. Bacterial predators consume bacteria and release nutrients in plant-available forms. Bacteria decompose organic matter, taking the nutrients from that dead plant material inside their bodies. Many species of bacteria are very well known as decomposers of toxic materials.
1. Beneficial Bacteria
Morphology can be used to differentiate different species. Higher diversity is desirable as a way to prevent growth of one particular species. If just one species is present, growing rapidly and take over all resources, that one species canot do all the functions that bacteria should perform. If a pathogen arrived, there would be little competition to prevent the disease organism from harming the plants. Thus, diversity is important to maintain.
Narrow-diameter bacterial filaments appear to have no space inside them, but rather, are just single pencil lines drawn through the soil or solution. Nonmycorrhizal plants tend to encourage actinobacteria around their root systems, possibly as a mechanisms to prevent mycorrhizal colonizations.