Sizing Marine Microbes With Scattered Light

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One of the most significant revolutions in the marine sciences in recent decades has been the characterization of the fundamental role that microbes play in both oceanic and global ecology. However, despite their significance, the assessment of population size spectra, considered to be an important character of marine ecosystems, has been problematic. The issue is compounded by the fact that more than 90% of marine microbes cannot be cultured. Over the last decade, Dr. Jaffe has been working on a next generation of instruments that show promise to characterize marine microbes using visible light. The central idea of the new instrument takes advantage of the fact that the light that is scattered at the non-forward angles contains information about the smallest spatial structures in the object. Since this light is not a major component of the light imaged in conventional optical microscopy, features of conventional images are insensitive to structures smaller than ~ 1 µm. Although more advanced methods can exceed this criteria, their use in a routine manner to size marine microbial populations is not straightforward. The PI requests funding to develop a new type of light microscope that can be used to characterize particles that are smaller than the wavelength of light. A successful demonstration that light microscopy can be used to systematically characterize sub-wavelength particles in the routine manner described here would be a significant milestone in the development of optical methods. As such, other fields of inquiry, such as cellular biology, would benefit from this methodology as the routine inference of sub wavelength cell structure has important ramifications for cell sorting, understanding cellular structure, as well as cell pathology.Broader Impacts:The proposed optical system and analysis methods could broadly impact marine microbial ecology, bio-optical oceanography, and potentially extend to other fields such as biomedicine. The project specifically contributes to graduate education/training through support of a PhD student. Outreach to high-school applications is also outlined. But most importantly, the potential project outcomes can be used in a broad range of other biological and marine-physics fields which employ optical methods to deal with very small objects.