Syntrophaceae

Key takeaways

Syntrophaceae belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Syntrophaceae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Syntrophaceae from memory before moving on to harder problems.

Reference excerpt

Syntrophaceae is a family of bacteria in the order Syntrophales. It comprises four genera: Syntrophus, Smithella, Desulfobacca and Desulfomonile. All members have rod-shaped cells and do not form spores. As gram-negative bacteria, the presence of a thin cell wall and a double membrane is notable. This bacterium usually forms red or pink colonies.

Metabolism Syntrophaceae are strict anaerobes, utilizing either respiratory or fermentative metabolism, and grow only in the presence of hydrogen/formate-utilizing partners in syntrophic relationships. They use simple organic molecules as electron donors, oxidizing substrates to either acetate or carbon dioxide. All are mesophilic and chemoorganoheterotrophic, except for Desulfomonile species, which can grow autotrophically on hydrogen and carbon dioxide. Some genera, such as Syntrophus and Smithella, can use crotonate as an electron acceptor for fermentative growth. Other genera like Desulfobacca and Desulfomonile can reduce sulfate, sulfite, and thiosulfate to sulfide, with Desulfomonile also able to reductively dehalogenate m-halogenated benzoates to their corresponding benzoate derivatives.

Genome sequencing The complete genome sequence of three members of this family has been analyzed:

Syntrophus aciditrophicus, strain SB, is 3,179,300 base pairs long, with 3,217 genes, 3,166 of which encode proteins. The G+C content is 51.5%. Desulfobacca acetoxidans, strain ASRB2, spans 3,282,536 base pairs, containing 3,022 genes (2,969 protein-coding and 54 RNA-coding). The G+C content is 52.9%. Desulfomonile tiedjei, strain DCB-1, is 6,500,104 base pairs long, consisting of one chromosome and a 26,923 bp plasmid, with 5,664 genes, 5,494 of which are protein-coding. The G+C content is 50.1%. What can be gathered from this information is that AprBA of Desulfobacca acetoxidans is closely related to the AprBA sequences of green sulfur bacteria and the AprBA of Desulfomonile tiedjei resembles the gram-positive type. Both genomes of these families contain single copies of the dissimilatory adenylyl sulfate reductase (AprBA) linked to the membrane-bound Qmo complex (QmoABC) and the dissimilatory sulfite reduction (DsrAB) linked to the DsrMKJOP complex. All of these are absent in the genome of Syntrophus aciditrophicus. By sequencing 16S rRNA gene from environmental samples (such as sewage sludge, sediment, or human gut) researchers can identify the presence and abundance of Syntrophales. This sequencing has become a rapid and reliable way to identify bacterial strains that may otherwise be difficult to distinguish using traditional culturing methods. Particularly due to the involvement this family of bacterium have with complex, anaerobic metabolic processes. By comparing the 16S rRNA sequence of an unknown strain to known sequences in databases, researchers can confirm whether it belongs to the Syntrophales or to a closely related group.

Ecology The four genera mentioned previously were isolated from a variety of environments, including freshwater, brackish, and marine habitats. Key strains include:

Syntrophus buswellii (strain SB): Initially isolated as part of a syntrophic coculture from anaerobic digester sludge in Urbana, Illinois, using benzoate as a substrate. A pure culture was later obtained using crotonate. Syntrophus aciditrophicus (strain SB): Isolated from secondary anaerobic digester sludge in Norman, Oklahoma, using crotonate in a syntrophic benzoate-degrading culture. Syntrophus gentianae (strain HQGö1): Isolated from anoxic sewage sludge in Göttingen, Germany, using hydroquinone or gentisate as substrates. Smithella propionica (strain LYP): Isolated from anoxic sewage sludge in Oregon, USA, with crotonate from a syntrophic propionate-degrading culture. Additional strains that are not involved in anaerobic degradation of organic compounds or coupled with methane formation include:

Desulfobacca acetoxidans (strain ASRB2): Isolated from granular sludge in a laboratory reactor using acetate as the sole carbon and electron source. Desulfomonile tiedjei (strain DCB-1): Isolated from a sewage sludge consortium degrading 3-chlorobenzoate. Desulfomonile limimaris (strain DCB-M): Isolated from sulfate-free medium with 3-chlorobenzoate as the electron acceptor and pyruvate/lactate as electron donors, from anoxic marine sediment.

References

Kuever, J. (2014). The Family Syntrophaceae. In: Rosenberg, E., DeLong, E.F., Lory, S., Stackebrandt, E., Thompson, F. (eds) The Prokaryotes. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-39044-9_269 Langwig, M. V., De Anda, V., Dombrowski, N. et al. (2022). Large-scale protein level comparison of Deltaproteobacteria reveals cohesive metabolic groups. ISME Journal, 16, 307-320. Oude Elferink SJWH, Akkermans-van Vliet WM, Bogte JJ, Stams AJM (1999) Desulfobacca acetoxidans gen. nov. sp. nov., a novel acetate-degrading sulfate reducer isolated from sulfidogenic granular sludge. Int J Syst Bacteriol 49:345–350 Shelton DR, Tiedje JM (1984) Isolation and partial characterization of bacteria in an anaerobic consortium that mineralizes 3-chlorobenzoate acid. Appl Environ Microbiol 48:840–84

Worked examples

Example 1 — a first encounter with Syntrophaceae

Start with the simplest possible case. Write down what Syntrophaceae claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Syntrophaceae before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Syntrophaceae ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Syntrophaceae

In research: Syntrophaceae appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Syntrophaceae in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Syntrophaceae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacteria families, Thermodesulfobacteriota, so understanding it makes those chapters shorter.
In everyday life: Look for Syntrophaceae outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Syntrophaceae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Syntrophaceae means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Syntrophaceae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Syntrophaceae in simple terms?

Syntrophaceae is a family of bacteria in the order Syntrophales. It comprises four genera: Syntrophus, Smithella, Desulfobacca and Desulfomonile.

Why does Syntrophaceae matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Syntrophaceae?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Syntrophaceae.