Bug of the Month: Diagnosing the 'Stress Bug'

In this month's wastewater microbiology spotlight, we take a look at irregular growth formations that indicate stressed systems

Bug of the Month: Diagnosing the 'Stress Bug'

While there’s no official morphotype name that we’re familiar with, the “irregular growth formations” microbe type recognition was passed on from the late Dr. Michael Richard. Based on his experience viewing thousands of wastewater samples over a 40-year career, he referred to these irregular growth formations as an indicator of stress somewhere within the system.

Over the last 10 years, we have seen this correlation often, based upon correlating conditions in plants viewed and their respective microbiology present. 

The “stress bug” appears to be a fairly reliable indicator of stress, however, it is important to note that there are many potential causes of stress which may likely produce these growth formations, including but not limited to very low dissolved oxygen/microaerophilic conditions, low pH, low nitrogen and inhibitory substances. 

It is common that irregular growth formations may be found on filamentous bacteria and within flocs in conditions of stress, and when these formations are present, these formations tend to proliferate at high abundance. The taxonomic properties of irregular formations is suspected to be of the Bacteriodes and/or Proteobacteria phylum. 

Most often, these formations stain Gram-negative, but in occasional instances have appeared Gram-positive. Generally, irregular growth formations are accompanied by other potential indicators of stress, such as dead or damaged filamentous bacteria, high dispersed growth, “dead bug” foams, flagellate blooms or lack of healthy higher life form organisms. Sometimes they’re accompanied by significant amounts of fungi or yeast. 

As with everything for practical wastewater microscopy applications, the context of the overall sample must be compared to any specific microbe types to help gain a big-picture diagnosis. Diagnosing stress under the microscope is generally straightforward, however, collaboration with operations personnel as to potential causes is needed for any general troubleshooting.

About the author: Ryan Hennessy is the principal scientist at Ryan Hennessy Wastewater MicrobiologyHe was trained and mentored by Dr. Michael Richard for over 10 years in wastewater microbiology, and serves as a microbiology services consultant. Hennessy is a licensed wastewater treatment and municipal waterworks operator in the state of Wisconsin and fills in as needed for operations at several facilities. He can be reached at ryan@rhwastewatermicrobiology.com. Hennessy's new book Wastewater Microbiology: Filamentous Bacteria Morphotype Identification Techniques, and Process Control Troubleshooting Strategies is now available on Amazon.


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