An unassuming bottle of PBS

The following post was inspired by my good friend jt and her blog Materialista.

On a trip to the SFMOMA earlier this year, I was captivated by this photo titled “Definitely Not Sterile” by Catherine Wagner. The photo is part of a series titled “Art & Science: Investigating Matter”, which also includes photos of -86°C freezers containing tissue samples from the Human Genome Project. (Interesting side note: Catherine Wagner later used the freezer photos as a skin for the interior walls of a fashion/design store in Kyoto, Japan.)

I stood in front of “Definitely Not Sterile” for several minutes. Other people meandering in the gallery must have been absolutely mystified about what I saw in this photo of a bottle labeled with tape.

What I love about art, and especially modern art, is its removal of an otherwise mundane object from its normal context, such that the object stands on its own – the object speaks to you differently. Such was the case with Catherine Wagner’s photo and myself on that day.


View above my lab bench, August 2005

The bottle was so intimately familiar, an object that had once been part of my everyday life as a bench scientist. As I stood in front of the photo, memories and information came rushing to my mind. Upon reflection, I realized that nearly a decade of lab training enabled me to derive all sorts of (perhaps trivial) information from the photo. Musing on these further started to bring to mind some random lab anecdotes. To borrow from a trite phrase, I may have left the lab, but the lab will never leave me…

1) Condensation. The bottle was recently removed from what was most likely a refrigerator set to 4°C. The PBS (phosphate buffered saline) solution might have been used for mammalian cell culture work, but only for final collection or harvesting of the cells and not splitting or passaging the cells since the bottle clearly indicates the PBS is “definitely not sterile”. Any fungal cells lurking in the non-sterile PBS would quickly outgrow the relatively slow growing mammalian cells and overtake the petri dish! PBS is used for many other purposes as well – I worked on budding yeast for my graduate research and used a combination of PBS and formaldehyde to fix (preserve) yeast cells for microscopy work.

2) “Definitely not sterile”. Bottles of PBS and other solutions are often autoclaved (i.e. heated up to 121°C in a large oven such that they are sterilized). After being cooled down to 4°C, the sterile buffer is ready to use for cell culture work. But in order to retain its sterility, the bottle must only be opened within a biosafety hood (inside of which is a sterile environment). This bottle was likely once sterile, but at some point opened outside the hood, is no longer sterile, and thus must be labeled as such. Usually it is sufficient to label it as “not sterile”, but whoever labeled this bottle clearly had a sense of humor.

3) “1X PBS”. Working concentration of PBS. Because PBS and other buffers are frequently used, they are often made up at 10X concentration, and then diluted to working concentration as needed.

4) “6/28/95”. I can’t make out the name (Sonnet? Sonrust?), but the date is likely the date on which this person diluted this stock of PBS. It is common practice to date and name your bottles, so that you can remember how “old” the solution is and identify which bottle is yours. It is in bad taste to use someone else’s solutions without first getting permission. It is in even poorer taste to completely use up someone else’s solution without getting permission and then leave the empty bottles on that person’s shelf. This has actually happened to me.


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