UV Resistance of bacteria from the Kenyan Marine cyanobacterium Moorea producens.

Thomas Dzeha,Dimitris Kardasopoulos,Constance Nyiro,J Grant Burgess,Joseph Mwafaida,Michael J Hall,David Mburu

doi:10.1002/mbo3.697

Thomas Dzeha, Dimitris Kardasopoulos + Show 5 more

Open Access

https://doi.org/10.1002/mbo3.697

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Abstract

UV resistance of bacteria isolated from the marine cyanobacterium Moorea producens has not been observed previously, findings which highlight how unsafe germicidal UV irradiation for sterilization of air, food, and water could be. Further, UV resistance of Bacillus licheniformis is being observed for the first time. This study focused on bacteria isolated from the marine cyanobacterium M. producens collected off the Kenyan coast at Shimoni, Wasini, Kilifi, and Mida. UV irradiance of isolates (302 nm, 70 W/m2, 0–1 hr) established B. licheniformis as the most UV resistant strain, with the following order of taxon resistance: Bacilli> γ proteobacteria > Actinobacteria. UV resistance was independent of pigmentation. The maximum likelihood phylogenetic distance determined for both B. licheniformis and Bacillus aerius relative to M. producens CCAP 1446/4 was 2.0. Survival of B. licheniformis upon UV irradiance followed first‐order kinetics (k = 0.035/min, R 2 = 0.88). Addition of aqueous extracts (2, 10, 20 and 40 mg/ml) of this B. licheniformis strain on the less resistant Marinobacterium stanieri was not significant, however, the commercial sunscreen benzophenone‐3 (BP‐3) positive control and the time of irradiance were significant. Detection of bacteria on M. producens filaments stained with acridine orange confirmed its nonaxenic nature. Although the chemistry of UV resistance in cyanobacteria has been studied in depth revealing for example the role of mycosporine like amino acids (MAAs) in UV resistance less is known about how bacteria resist UV irradiation. This is of interest since cyanobacteria live in association with bacteria.

Highlights

The oceans are recipients of high solar radiation and an understanding of the adaptations of organisms therein toward the deleterious effects of UV radiation can aid the search for novel photoprotective agents
The pantropic marine cyanobacterium M. producens is ubiquitous in the Western Indian Ocean marine ecosystem
The isolation of bacteria from the Kenyan M. producens is consistent with the nonaxenic nature of the cyanobacterial isolates obtained in this study (Figure 1) and with established literature (Engene et al, 2012)

Summary

| INTRODUCTION

The oceans are recipients of high solar radiation and an understanding of the adaptations of organisms therein toward the deleterious effects of UV radiation can aid the search for novel photoprotective agents. Cyanobacteria fulfill vital ecological functions in the world’s oceans, being important contributors to global carbon and nitrogen budgets They are arguably the most successful group of microorganisms on earth, having existed for the last 3 billion years. Mycosporines and MAAs are UV-absorbing small molecules (λmax = 310–360 nm) and are synthesized by fungi and eukaryotic micro-and macroalgae (Bandaranayake, Bemis, & Bourne, 1996; Shick & Dunlap, 2002) Their success in preventing UV-induced skin damage in vivo has led to their commercialization, for example in the products Helioguard 365 and Helionori sunscreens to protect against UV-A (Balskus & Walsh, 2010; De la Coba et al, 2009; Siezen, 2011).

| MATERIALS AND METHODS

Findings

| DISCUSSION