Microscope-based light gradient generation for quantitative growth studies of photosynthetic micro-organisms

Abstract

Photosynthetic micro-organisms are equipped with molecular machineries that are designed to transform light into chemical or bioenergy, and help shape and balance the ecosystem of all life forms on earth....

A high throughput array microhabitat platform reveals how light and nitrogen colimit the growth of algal cells

“…We propose a general colimitation growth model for algal cells subjected to both physical and chemical parameters. Previous work in our labs showed that algal cell growth followed Monod growth kinetics when grown with either a nitrogen or a light intensity gradient alone 39 , 51 . Here, we hypothesized that algal growth response to light or nitrogen was described by Monod kinetics individually, and the synergistic effect of light and nitrogen on algal growth was reflected in a multiplicative term of the model: …”

“…1 A and Ref. 51 ). Briefly, the light intensity gradient at the location of the array microhabitat was created by placing a half-moon shaped mask directly below the field iris of an Olympus IX81 microscope.…”

“…( D ) Light intensity gradient in the x-direction as measured by grayscale values of bright field images of the microhabitat array. The PAR (µmol·m –2 ·s –1 ) values were converted from grayscale values using a linear relationship obtained in a previous work 51 . Mean light intensity at the vertical centerline of each column of microhabitats was used as the light intensity for the column.…”

“…1 D). PAR values were converted from the grayscale values measured from brightfield images of the light intensity gradient captured with a CCD camera as described previously 51 . The light intensity of each column was calculated as the average across the width of the microhabitats in that column, as cells were observed to swim freely within single habitats.…”

“…4 ) and our previous work where cell growth response was studied under dual nitrogen and phosphorous gradients 48 . Under a single nutrient or light gradient, we used a microfluidic platform to reveal that algal cell growth followed a Monod growth kinetic model 39 , 51 . Under a dual nitrogen and phosphorous gradient, a multiplicative model fitted to the growth data showed the colimitation by two nutrients (Supplementary Information).…”