Plant root excretions called exudates are one of the three main staples of food for beneficial, symbiotic bacteria. Therefore large colonies are gathered in the rhizosphere, the area surrounding plant roots. In the rhizophere there are additional foods. The plant cell’s root-tip sheds cell parts during its development and growth, which holds nutritional value for the bacteria when decomposed. The third most important food for bacteria is the animal and plant organic compounds that set the bacteria decomposing the larger compounds. This is the dynamo behind the nitrogen and carbon cycle.

Food Groups of Bacteria

Organic compounds are a composite of long complex molecules. Like beads on a necklace, these complexes are attached end to end. The individual beads are made up of small molecules containing carbon.  Bacteria decompose the carbon complex bonds between each bead along certain points in the chain. So smaller chains are created made up of simple sugars, fats and amino acids. These 3 classes of substances are the fundamental groups of food bacteria will need to support themselves. Bacteria employ digestive enzymes to snap the bonds keeping the beads in the carbon necklace together. This all takes place outside of the bacteria prior to consumption. Many different types of digestive enzymes are produced  and implemented by these microbes. During their 3 billion years of evolution here on Earth, bacteria have adapted so well, they are able to digest organic as well as inorganic materials. What amazes me is that they can so effectively digest all sorts of materials while maintaining the integrity of their own cell walls.

Nitrogenous Bacterial Food

Different species of bacterias live on different food resources, according to what’s accessible. Nearly all bacteria are happier decomposing fresh vegetative materials, that us composers call “greens”, Nitrogenous Materials. You probably have heard of the Carbon/Nitrogen (C/N) ratio when learning how to create compost. A 20/1 ratio is normally recommended for the balance of tough carbon fibers vs soft nitrogenous material. Bacteria use the carbon for producing energy and the nitrogen for protein production. Composters refer to the carbon (tree leaves and stems) as “browns”, Carbonaceous Material. Before it can be converted into manageable carbon chains for energy, other microbes, normally fungus, need to reduce it. If there is not enough soft, green, nitrogenous materials in the compost mix we end up with little nutrition. Many times we gauge the quality of our compost by the percentage of NPK within. But if their is not enough brown, carbonaceous material in the compost mix, there will not be enough carbohydrates to support the energy level of the microbes at work. Most often it is the dry tree leaves taht provide space and aeration to the compost pile. With little or no air, anaerobic bacteria take over which are pathogenic and harmful to the microbe community, not to mention plants and humans.

Bacterial Food Ingestion

Bacteria are small and must ingest even smaller pieces of organic matter. So how does a bacteria swallow an elephant? Actually they don’t swallow anything. Bacteria ingest carbohydrates and nutrition right through their cell walls. Their cellular surfaces are made up of proteins that help with this molecular transportation. Within a bacteria’s cell will be a mixture of sugars, proteins, carbons, and charged ions. Molecular transfer through the cellular membrane is actually achieved in a few different ways. Membrane transfer is really an intriguing topic. It is a complex procedure supported by charged electrons found on each side of the tissue layer’s surface. But it is beyond the scope of this article to outline the driving force of osmotic barriers. Yet, we ought to understand and value just how bacteria eat. The principal concern for us horticulturist is that bacteria decompose organic matter into smaller, electrostatic charged particles externally, after which it is carried through cell membranes, ready to be assimilated. When inside the bacteria, the elements are locked up, only being released after death and decomposition. This is part of the fixation in the nitrogen cycle.