Quantitative insights into the cyanobacterial cell economy

Abstract

Phototrophic microorganisms are promising resources for green biotechnology. Compared to heterotrophic microorganisms, however, the cellular economy of phototrophic growth is still insufficiently understood. We provide a quantitative analysis of light-limited, light-saturated, and light-inhibited growth of the cyanobacterium Synechocystis sp. PCC 6803 using a reproducible cultivation setup. We report key physiological parameters, including growth rate, cell size, and photosynthetic activity over a wide range of light intensities. Intracellular proteins were quantified to monitor proteome allocation as a function of growth rate. Among other physiological acclimations, we identify an upregulation of the translational machinery and downregulation of light harvesting components with increasing light intensity and growth rate. The resulting growth laws are discussed in the context of a coarse-grained model of phototrophic growth and available data obtained by a comprehensive literature search. Our insights into quantitative aspects of cyanobacterial acclimations to different growth rates have implications to understand and optimize photosynthetic productivity.

Dynamic macromolecular composition and high exudation rates inProchlorococcus

“…Assuming that the ribosomes of phytoplankton and bacteria have similar 395 maximal rates of protein production (chain elongation), this suggests that phytoplankton ribosomes are 396 working at a higher relative capacity. In phytoplankton, a significant amount of protein production 397 needs to be invested in maintaining the photosynthetic apparatus, for example in the replacement of 398 the core proteins (Zavřel et al 2019). An alternative (but non-exclusive) explanation is that 399 heterotrophic bacteria (primarily copiotrophic ones) maintain more ribosomes than needed, using the 400 "spare" production capacity to allow rapid response to changes in growth conditions.…”

Stoichiometry of two plant glycine decarboxylase complexes and comparison with a cyanobacterial glycine cleavage system

“…We also calculated from the proteome data of Gärtner et al (2019) that the GCS proteins would collectively represent approximately 0.07% (w/w) of the total protein in Synechocystis (Table 1) and a larger fraction in the soluble protein fraction. Similar levels can be derived from proteome data of Synechocystis provided by Jahn et al (2018) and Zavřel et al (2019). With a mean protein content of about 300 mg ml -1 for Synechocystis (Jahn et al , 2018), this fraction corresponds to a combined concentration of the GCS proteins of about 0.2 mg ml -1 , which is surprisingly close to and even somewhat less than the recently reported GCS concentration in heterotrophic Arabidopsis cells (Fuchs et al , 2019) and 2.5-fold higher than the above mentioned dissociation threshold of 0.08 mg ml -1 for the pea leaf GDC (Oliver et al , 1990).…”

“…This is critical only for the Synechocystis H-protein, which likely is largely underestimated by Hi3 quantification due to the inherent difficulties in the quantification of small proteins, represented by very few tryptic peptides. This can be seen from the fact that a similar ratio of approximately 1L 2 -0.2P 2 -0.4T (H-protein could not be quantified) can be calculated from the independent Synechocystis proteome data of Zavřel et al (2019).…”

Towards a quantitative assessment of inorganic carbon cycling in photosynthetic microorganisms

“…Such values represent a higher PQ variation than reported previously for Synechocystis . However, in previous works light of lower intensity and different wavelength was used. As mentioned above, in Synechocystis blue light preferentially affects PSI, resulting in cyclic electron flow .…”