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Coral disease is a growing problem for coral reefs globally and diseases have been linked to thermal stress, excess nutrients, overfishing and other human impacts. The Red Sea is a unique environment for corals with a strong environmental gradient characterized by temperature extremes and high salinities, but minimal terrestrial runoff or riverine input and their associated pollution. Yet, relatively little is known about coral diseases in this region. Disease surveys were conducted at 22 reefs within three regions (Yanbu, Thuwal, Al Lith) in the central Red Sea along the Saudi Arabian coast. Surveys occurred in October 2015, which coincided with a hyperthermal-induced bleaching event. Our objectives were to 1) document types, prevalence, and distribution of coral diseases in a region with minimal terrestrial input, 2) compare regional differences in diseases and bleaching along a latitudinal gradient of environmental conditions, and 3) use histopathology to characterize disease lesions at the cellular level. Coral reefs of the central Red Sea had a widespread but a surprisingly low prevalence of disease (<0.5%), based on the examination of >75,750 colonies. Twenty diseases were recorded affecting 16 coral taxa and included black band disease, white syndromes, endolithic hypermycosis, skeletal eroding band, growth anomalies and focal bleached patches. The three most common diseases were Acropora white syndrome (59.1% of the survey sites), Porites growth anomalies (40.9%), and Porites white syndrome (31.8%). Sixteen out of 30 coral genera within transects had lesions and Acropora, Millepora and Lobophyllia were the most commonly affected. Cell-associated microbial aggregates were found in four coral genera including a first report in Stylophora. Differences in disease prevalence, coral cover, amount of heat stress as measured by degree heating weeks (DHW) and extent of bleaching was evident among sites. Disease prevalence was not explained by coral cover or DHW, and a negative relationship between coral bleaching and disease prevalence was found. The northern-most sites off the coast of Yanbu had the highest average disease prevalence and highest average DHW values but no bleaching. Our study provides a foundation and baseline data for coral disease prevalence in the central Red Sea, which is projected to increase as a consequence of increased frequency and severity of ocean warming., Competing Interests: The authors have declared that no competing interests exist.

Deserts, such as those found in Saudi Arabia, are one of the most hostile places for plant growth. However, desert plants are able to impact their surrounding microbial community and select beneficial microbes that promote their growth under these extreme conditions. In this study, we examined the soil, rhizosphere and endosphere bacterial communities of four native desert plants Tribulus terrestris, Zygophyllum simplex, Panicum turgidum and Euphorbia granulata from the Southwest (Jizan region), two of which were also found in the Midwest (Al Wahbah area) of Saudi Arabia. While the rhizosphere bacterial community mostly resembled that of the highly different surrounding soils, the endosphere composition was strongly correlated with its host plant phylogeny. In order to assess whether any of the native bacterial endophytes might have a role in plant growth under extreme conditions, we analyzed the properties of 116 cultured bacterial isolates that represent members of the phyla Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. Our analysis shows that different strains have highly different biochemical properties with respect to nutrient acquisition, hormone production and growth under stress conditions. More importantly, eleven of the isolated strains could confer salinity stress tolerance to the experimental model plant Arabidopsis thaliana suggesting some of these plant-associated bacteria might be useful for improving crop desert agriculture., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Natural products have been used for medical applications since ancient times. Commonly, natural products are structurally complex chemical compounds that efficiently interact with their biological targets, making them useful drug candidates in cancer therapy. Here, we used cell-based phenotypic profiling and image-based high-content screening to study the mode of action and potential cellular targets of plants historically used in Saudi Arabia's traditional medicine. We compared the cytological profiles of fractions taken from Juniperus phoenicea (Arar), Anastatica hierochuntica (Kaff Maryam), and Citrullus colocynthis (Hanzal) with a set of reference compounds with established modes of action. Cluster analyses of the cytological profiles of the tested compounds suggested that these plants contain possible topoisomerase inhibitors that could be effective in cancer treatment. Using histone H2AX phosphorylation as a marker for DNA damage, we discovered that some of the compounds induced double-strand DNA breaks. Furthermore, chemical analysis of the active fraction isolated from Juniperus phoenicea revealed possible anti-cancer compounds. Our results demonstrate the usefulness of cell-based phenotypic screening of natural products to reveal their biological activities.

Endozoicomonas bacteria were found highly associated with the coral Stylophora pistillata, and these bacteria are also ubiquitously associated with diverse corals worldwide. Novel Endozoicomonas-specific probes revealed that Endozoicomonas bacteria were abundant in the endodermal tissues of S. pistillata and appear to have an intimate relationship with the coral.