Hyphomicrobium - easy to see under the microscope & a common wastewater organism

From https://www.studyblue.com/notes/note/n/proteobacteria/deck/12403526

Hyphomicrobium sp. are comomn in wastewater plants and very well discussed for their indicating denitrification. Hyphomicrobium are often noted because of their unique apperance and reproduction by budding. You have a "mother", a non-motile cell with a cylindrical stalk protruding from the floc. The "daughter" cell that eventually breaks away from the mother is motile bacteria (by way of a bacterial flagella) that allows for the daughter cell to colonize new areas. The stalk can be up to 3 um long so it can be observed with a phase contrast microscope under 400x magnification.

So what does having Hyphomicrobium mean to operating a WWTP? Looking at Hyphomicrobium metabolism:

• ​Use methanol and other short chain soluble organic compounds as an energy source. Even if these compounds are not present in your influent, they are often formed as bacteria degrade higher molecular weight organics.
• Prefer to use oxygen for respriation but are also very capable of using nitrate and nitrite as an alternative electron acceptor.
• Potential - not fully documented - to grow on energy provided by manganese oxidation. (This is still being discussed)
• Mesophilic with individual species in the Hyhomicrobium genus having different nitrate reductases, salinity toleranes, and organic energy sources.

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So if you see an increase in Hyphomicrobium  in your system, you may have:

• More methanol or short-chain soluble organics
• Higher nitrate and/or lower D.O. (remember lower DO can exist inside the floc)

Overall Hyphomicrobium  are a common water bacteria that can increase in populations when conditions are sufficient. If you are required to remove Nitrate/Nitrite for effluent permits, seeing Hyphomicrobium can be a very good indication of healthy denitrification.