The heterotrophic bacteria, Also called organotrophs, they are microorganisms that synthesize their own biomolecules from complex carbonaceous organic compounds, although they can capture inorganic elements other than carbon. Some need to parasitize higher organisms in order to survive.
Heterotrophic bacteria are classified into photoheterotrophs and chemoheterotrophs. Both use organic compounds as a carbon source, but differ in that the former use light as an energy source and the latter use chemical energy..
Heterotrophic bacteria are present in numerous ecosystems, such as soils, water, marine muddy snow, among others, participating in the ecological balance. They can also be found parasitizing higher organisms, such as plants, animals or humans, either as pathogens or as opportunists in a symbiotic relationship..
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It has been observed in nature that the existence of different types of bacteria makes the life of ecosystems possible, since the products generated by one are used by others in a chain. These bacteria are strategically distributed, almost always stratified.
For example, it has been seen that aerobic heterotrophic bacteria often appear together with cyanobacteria (photoautotrophic bacteria that release oxygen).
In this sense, aerobic heterotrophs and aerobic autotrophs can use oxygen, in turn creating anaerobic conditions in the deeper layers where anaerobic bacteria are found..
Depending on characteristics such as the type of fuel they use to survive, heterotrophic bacteria can be classified into different groups.
They are bacteria that under anaerobic conditions are capable of reducing sulfate (sulfuric acid salt or esters) without assimilating it. They only use it as a final electron acceptor in the respiratory chain.
These bacteria help in the degradation of organic matter and are found in various ecological niches such as fresh waters, sewer waters, salt waters, hot springs, and geothermal areas. Also in sulfur deposits, oil and gas wells, as well as in the intestines of mammals and insects.
They are anaerobic bacteria that break down organic polymers (cellulose and hemicellulose) into small molecules so that they can be absorbed by cell membranes. To do this, they have a system of enzymes called hydrolases (endocellulase, excocellulase and cellobiases).
After hydrolysis, various organic acids are formed such as lactic acid, propionic acid, acetic acid, butanol, ethanol, and acetone. These are then converted into methane gas.
They are bacteria that participate in the catabolic degradation of nitrogenous compounds under anaerobic conditions, with the production of compounds with an unpleasant odor, hence their name (putrefactive). This process generates the carbon and nitrogen they need for their development..
These bacteria are characterized by being straight, mobile bacilli with a polar flagellum. They are facultative anaerobes: in anaerobiosis they carry out the photosynthesis process, but in aerobiosis they do not carry it out.
These bacteria photoassimilate a great diversity of organic compounds such as sugars, organic acids, amino acids, alcohols, fatty acids and aromatic compounds..
They are filamentous bacteria that can develop as photoautotrophs, chemohetrotrophs or photoheterotrophs.
Various species enter here that can form part of the usual microbiota of higher organisms, or act as pathogens of these.
Both chemoheterotrophic and chemoautotrophic bacteria use chemical energy to live. However, they differ in that chemoheterotrophs are dependent organisms, since they need to parasitize other higher organisms to obtain the organic compounds necessary for their development..
This characteristic differentiates them from chemoautotrophic bacteria, which are totally free-living organisms (saprophytes), which take simple inorganic compounds from the environment to perform their vital functions..
For their part, photoheterotrophs and photoautotrophs are similar in that they both use sunlight to convert it into chemical energy, but they differ in that photoheterotrophs assimilate organic compounds and photoautotrophs do so with inorganic compounds..
On the other hand, chemoheterotrophic bacteria differ from chemoautotrophic bacteria in the habitat where they develop.
Chemoheterotrophic bacteria generally parasitize higher organisms to live. On the other hand, chemoautotrophic bacteria can withstand extreme environmental conditions..
In these environments, chemoautotrophic bacteria get the inorganic elements they need to live, substances that are generally toxic to other microorganisms. These bacteria oxidize these compounds and turn them into more environmentally friendly substances..
Heterotrophic bacteria only assimilate complex organic compounds already preformed to be able to synthesize the biomolecules necessary for their development. One of the carbon sources most used by these bacteria is glucose.
In contrast, autotrophic bacteria simply need water, inorganic salts, and carbon dioxide to get their nutrients. That is, from simple inorganic compounds they can synthesize organic compounds.
However, although heterotrophic bacteria do not use carbon dioxide as a carbon source, nor as the last electron acceptor, on some occasions they can use it in small amounts to carry out carboxylations in certain anabolic and catabolic pathways..
In some ecosystems, samples can be taken to study the population of photoautotrophic and photoheterotrophic bacteria. For this, the microscopy technique based on epifluorescence is used: Fluorochrome such as primulin and excitation filters for blue and ultraviolet light are used..
Heterotrophic bacteria do not stain with this technique, while autotrophs take on a bright whitish-blue color, and the auto-fluorescence of the bacteriochlorophyll is also noted. The heterotrophic count is obtained from the subtraction of the total count of bacteria minus the autotrophs..
In this sense, the bacteria that cause diseases in humans, animals and plants belong to the group of chemoheterotrophic bacteria.
Autotrophic bacteria are saprophytic and do not cause disease in humans, because they do not need to parasitize higher organisms to live.
The bacteria belonging to this group are always photosynthetic, since the rest of the microorganisms that share this classification are eukaryotic algae..
Sulfur bacteria are generally photoautotrophic, but can sometimes grow photoheterotrophically. However, they will always require small amounts of inorganic material (HtwoS), while the non-sulfurous ones are photoheterotrophs.
Among the photoheterotrophic bacteria we find the non-sulphorous red bacteria, such as the bacteria of the family Bradyrhizobiaceae, gender Rhodopseudomonas.
On the other hand, there are non-sulfurous green bacteria, as well as heliobacteria.
They are facultative chemoautotrophs, that is, they normally use molecular hydrogen as an energy source to produce organic matter, but they are also capable of using a certain number of organic compounds for the same purpose..
Family bacteria Frankiaceae, group Rhizobiaceae and the genres Azotobacter, Enterobacter, Klebsiella Y Clostridium. These microorganisms participate in the fixation of elemental nitrogen.
Most can do it independently, but some need to establish symbiotic relationships with rhizobiaceae and legumes.
This process helps the soil renewal, converting elemental nitrogen into nitrates and ammonium, which are beneficial as long as the latter are in low concentrations in the soil..
Nitrate and ammonium can then be absorbed by plants, such that these bacteria are extremely important in nature. Rhizobia are the most used bacteria in agriculture, and are part of biofertilizers.
Pepto-streptococcus, Propionibacterium, Clostridium, Micrococcus Y Bacteroides. These bacteria have the property of interacting with bacteria belonging to the Enterobacteriaceae family..
Bacteroides sp, Clostridium sp, Bifidobacterium sp, Sphaerophorus sp, Fusobacteium sp, Veillonella sp, Y Peptococcus sp, among others.
In this category are species of the genus Clostridium: C. botulinum, C. perfringens, C. sporongenes, C. tetani and C. tetanomorphum. Likewise, some species of the genera Fusobacterium, Streptococcus, Micrococcus Y Proteus.
All the bacteria that cause infectious diseases in man and animals are found here. Also those that are part of the usual microbiota.
Examples: families Streptococaceae, Staphylococaceae, Enterobacteriaceae, Mycobacteriaceae, Pasteurellaceae, Neisseriaceae, Pseudomonadaceae, among many others.
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