What are photosynthetic bacteria (PSB)?

Photosynthetic bacteria (hereafter referred to as PSB) are indigenous to rice fields, but they can be found anywhere with accumulated water and organic matter, not just in rice fields.

PSB prefer bright places with strong ultraviolet rays and no oxygen. They thrive at temperatures between 25-35°C and in pH ranges of 6-9 (they are strong in alkaline conditions but weak in acidic ones).

Using light energy, PSB synthesizes amino acids by assimilating carbon from organic acids such as mercaptans and butyric acids, as well as from fatty acids, carbon dioxide, and hydrogen sulfide. They also fix nitrogen from the air and convert it into nitrogen compounds.

Because PSB can neutralize hydrogen sulfide and harmful organic acids, they are sometimes used to prevent gas buildup in rice fields, thereby aiding in rice harvests.

PSBs are divided into three groups:

1. Red non-sulfur bacteria
   These bacteria consume organic acids and hydrogen sulfide. They can grow even in the presence of oxygen, making them relatively easy to cultivate.

2. Red sulfur bacteria
   These bacteria feed on hydrogen sulfide but do not grow well in the presence of oxygen.

3. Green sulfur bacteria
   These green photosynthetic bacteria consume hydrogen sulfide and do not grow at all in the presence of oxygen, making them very difficult to cultivate. An example is the “Tane-mizu” (Seed Water) sold by Nippon Dobutsu Yakuhin.

Cultivation difficulty increases in the order of 1, 2, and 3.

PSBs become more powerful through symbiosis with other bacteria.

Effects of coexisting photosynthetic bacteria and Bacillus megaterium under aerobic conditions:

• Nitrogen fixation
  The amount of nitrogen fixed over 8 days increases significantly when PSB coexist with other bacteria compared to when they exist alone.

When PSBs coexist with Bacillus subtilis (a type of Bacillus) and Bacillus subtilis natto, they exchange organic acids and energy (ATP), which enhances their ability to fix atmospheric nitrogen (producing nitrogen fertilizer). Their nitrogen-fixing ability is highest when coexisting with Bacillus megaterium, commonly found in compost. Additionally, their nitrogen-fixing ability increases when coexisting with lactic acid bacteria.

When PSB coexist with yeast and natto bacteria, they can grow even in the presence of oxygen.

Purple sulfur bacteria cannot grow or fix nitrogen in the presence of oxygen, but they can grow when yeast is nearby. This occurs because the yeast consumes oxygen, creating an anaerobic state around them. At this time, the PSB turn a hazy purple color. It is often mistakenly believed that a deeper reddish color of PSB is better, but there is no causal relationship between their effectiveness and color. Additionally, natto bacteria secrete a viscous substance around their bodies to create an anaerobic state, which also allows PSB to grow.

PSB die quickly when sown in fields, but actinomycetes feed on their dead particles and proliferate, suppressing Fusarium, a disease-causing agent in crops. Therefore, PSB are useful even when dead.

Benefits of Photosynthetic Bacteria (PSB):

Why does adding PSB to ponds and aquariums produce various beneficial results?

In nature, PSB live in rice fields, sewers, drains, cesspits, and similar environments. They feed on organic matter, particularly organic acids, fatty acids, hydrogen sulfide, and other substances that are generally considered malodorous and unpleasant to humans.

You may wonder why PSB thrive on smelly substances if they themselves have an odor. Please understand that the terrible smell emitted by the PSB culture medium is not actually produced by the PSB, but by other bacteria that grow alongside them. PSB are not smelly bacteria.

Many of the odors we perceive as bad smells are classified as nuisances and are not particularly welcomed by various organisms living in the water. However, these substances appear to be a welcome treat for PSBs.

Even on land, in facilities such as pig farms and chicken coops where complaints about foul odors from neighbors are constant, it is known that spraying PSB bacteria liquid directly or mixing it with drinking water clearly improves the effectiveness of odor control.

PSB is a cost-effective odor control agent that is highly valued. Additionally, the use of PSB in environmental conservation, which will be essential in the future, has been clarified and is beginning to be introduced in various fields.

What happens when you put PSB in a tank?

As you know, there are microorganisms called nitrifying bacteria living in aquariums, which convert the highly toxic ammonia excreted by the creatures in the tank into nitrite and then into less toxic nitrate. It is no exaggeration to say that the peace of the aquarium is brought about by nitrifying bacteria. Nitrifying bacteria can be found in all places in an aquarium, but they live in the highest density and work most efficiently in the filter tank or filtration device.

In fact, the bottom sand has a purification function that is not inferior to that of the filter tank. Even without a filtration system, as long as a moderate water flow caresses the surface of the bottom sand, the nitrification function is thought to be maintained. In nature, there are no special areas dedicated to nitrifying bacteria, such as filter tanks. Various microorganisms other than nitrifying bacteria also live in the bottom sand, making it a place where a wide variety of biological reactions take place, from the decomposition of organic matter, which is the first step in nitrification, to denitrification, which is the final process.

Can PSB replace nitrifying bacteria?

There is no doubt that PSB consume ammonia, but since there is a correlation between the amount of ammonia and the number of PSB bacteria, we cannot conclude that PSB can simply replace nitrifying bacteria. It is better to think of PSB as helping to break down ammonia, which was originally the sole responsibility of ammonia-oxidizing bacteria, one of the nitrifying bacteria. It is a bit of a dangerous leap to think that ammonia-oxidizing bacteria are unnecessary if you add PSB.

In an emergency situation where the activity of ammonia-oxidizing bacteria slows down for some reason, resulting in an increase in ammonia in the breeding water, PSB can act as a helper while waiting for the nitrifying bacteria to recover. Similarly, during the maturation period when setting up an aquarium, the ammonia-oxidizing bacteria have not yet increased sufficiently and a dangerous period of high ammonia concentrations will continue for some time, so it may be possible to rely on PSB for help during such times.

Thoughts on Bacteria

What are bacteria made of? Since bacteria are living organisms, their bodies must be composed of proteins.

The basic components of proteins are the four elements: carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). These elements form the acronym “CHON,” which is a helpful way to remember them.

No matter how beneficial bacteria are, when they die, they break down into these four elements. In most cases, the dead bacteria become food for other bacteria in the aquarium and are recycled as material to build their bodies.

Nitrogen (N) is an essential component of protein, so it is eventually reused as material in the bodies of other organisms within the food chain.

Recent studies have shown that more than 70% of human health is related to intestinal bacteria. Maintaining a healthy intestinal environment can largely guarantee our overall health. Most intestinal bacteria are descendants of soil bacteria and enter the body through the mouth.

Tracing the origins of many microorganisms living in an aquarium, we find that they are soil bacteria that entered the aquarium along with dust. In terms of their origins and functions, the world of microorganisms in an aquarium has similarities to that of intestinal bacteria.

Where is the place for PSBs?

PSB sometimes form symbiotic relationships with other soil bacteria, allowing for much more efficient production than if they lived alone.

As mentioned above, PSB carcasses serve as food for actinomycetes, a type of soil bacteria, increasing their numbers. Actinomycetes control pathogens in cultivated land and prevent plant diseases. As their numbers increase, plants and crops become less susceptible to disease. Spreading PSB on cultivated land results in healthier crops and higher yields.

The antibiotic streptomycin, developed from a strain of Streptococcus (a type of actinomycete), was a specific treatment for pulmonary tuberculosis, once feared as an incurable disease in Japan.

Many people are also familiar with Bifidobacteria, a well-known type of intestinal bacteria. Increasing the number of Bifidobacteria improves the intestinal environment. There is a strong relationship between our health and the density of Bifidobacteria, leading many to focus on increasing their numbers.

Interestingly, bifidobacteria are classified as relatives of actinomycetes.

If there are bacteria similar to bifidobacteria in an aquarium, maintaining the aquarium environment and raising the aquarium inhabitants may be significantly influenced by their presence.

Significance of Adding PSB to Aquariums

PSB not only improve the aquarium environment through their metabolism but also, even after death, the components in their bodies support the growth and activity of other beneficial microorganisms in the aquarium.

This is the very significance of adding PSB to the aquarium.