Bio-Inspired Molecular Catalysts for Water Oxidation

The catalytic tetranuclear manganese-calcium-oxo cluster in the photosynthetic reaction center, photosystem II, provides an excellent blueprint for light-driven water oxidation in nature. The water oxidation reaction has attracted intense interest due to its potential as a renewable, clean, and environmentally benign source of energy production. Inspired by the oxygen-evolving complex of photosystem II, a large of number of highly innovative synthetic bio-inspired molecular catalysts are being developed that incorporate relatively cheap and abundant metals such as Mn, Fe, Co, Ni, and Cu, as well as Ru and Ir, in their design. In this review, we briefly discuss the historic milestones that have been achieved in the development of transition metal catalysts and focus on a detailed description of recent progress in the field.

Photosynthetic Reaction-Center/Graphene Biohybrid for Optoelectronics

Photosynthetic reaction center proteins (RC) purified from purple bacterial strains were deposited on graphene layer prepared by liquid phase exfoliation and light-induced resistance change was measured. By measuring the temperature dependence of the resistance change of the bare and RC covered graphene and comparing with the one inactivated by protein unfolding, two effects were possible to separate. One of them is the resistance change due to temperature effect. The other one clearly indicates a possible electric/electronic interaction between the charge flow in the graphene and the light-induced charge pair within the protein, which is, essentially, different in the open (dark, PBPheo) and closed (light, P+BPheo−) states. These results provide useful information for designing hybrid bio-photonic devices which are able to absorb and convert light energy.

The role of anoxygenic phototrophs in the Baltic Sea

<p>Both oxygenic and anoxygenic phototrophic bacteria (OPB and APB, respectively) are widely distributed in the ocean and play significant roles in carbon cycle and marine productivity. These organisms capture light as energy source via chlorophyll or bacteriochlorophylls-based photosystems. While OPB are relatively well studied, information on APB is rather scarce although they have been shown abundant in some ocean ecosystems and may play an important role in oxygen depleted environments. Here, we investigate the spatial profile of OPB and APB, gene abundance and expression of the key functional marker gene <em>pufM </em>(APB specific photosynthetic reaction center subunit M), in one fjord and three basins of the Baltic Sea using 16S rRNA amplicon sequencing and qPCR. Among the microbial community, abundances of OPB and APB were found to be similar thus emphasizing a potential importance of APB, with APB representing 1.6-17.5% and OPB representing 0.5-20%. Among APB, we identified eleven different orders, with <em>Rhodobacterales</em> being quantitatively dominant. The identified seven orders of OPB were dominated by <em>Synechococcales</em>. OPB were more abundant than APB in surface waters (<8m), while APB were comparably more abundant in deeper waters. Besides a depth-dependent distribution, we observed an impact of salinity on the distribution of APB and OPB, both of which being suggestive of distinct niches for those primary producer clades. <em>pufM</em> gene abundance ranged from 10<sup>4</sup> to 10<sup>9</sup> copies/L, with highest counts detectable in the mixed layer (<40m), however, even in deeper waters where gene abundances decreased APB <em>pufM</em> gene expression was high with up to 10<sup>4</sup> copies/L. These results indicate APB may play a more important role in marine primary productivity which has been underestimated before. </p>

Effects of Bacterial Leaf Blight on Photosynthesis and Chlorophyll a Fluorescence in Susceptible and Resistant Rice Cultivars

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is a serious disease affecting rice. Understanding of the effects of this disease on photosynthesis and chlorophyll (Chl) a fluorescence is important in rice management. We studied the effect of BLB on enzyme activities, photosynthetic rate (Pn) and Chl a fluorescence transient in susceptible Neiwuyou 8015 and resistant Shenzhou 98 rice cultivars. BLB had a negative effect on rice net photosynthesis (Pn) and stomatal conductance (Gs). Superoxide dismutase (SOD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) activities, malondialdehyde (MDA) contents were increased while Chl content was decreased, indicating that rice photosynthetic functions were damaged by BLB. The effect of BLB on photosynthesis was greater in susceptible rice than in resistant rice. A significant difference of Chl a fluorescence transient curves was observed between BLB treatments and healthy ones. Parameters measured in transient rice Chl a fluorescence showed the photosynthetic reaction center was inactive after BLB. These findings will help in evaluating rice resistance and may be useful for rice disease management. © 2021 Friends Science Publishers