Cooperation Between Photosynthetic and Antioxidant Systems: An Important Factor in the Adaptation of Ulva prolifera to Abiotic Factors on the Sea Surface

Large-scale green tides have occurred continuously in the Yellow Sea of China from 2007 to 2018, and the causative species of the Yellow Sea green tide (YSGT) is Ulva prolifera. The thalli form floated thallus mats, and the thalli from different layers of the thallus mat suffer significantly different environmental conditions. In the present study, the environmental conditions of the surface layer (SL), middle layer (ML), and lower layer (LL) of the thallus mat from mid-June (Stage I) to mid-July (Stage II) were simulated. Photosynthetic traits and antioxidant systems were measured. The results showed that (1) photoprotective [non-photochemical quenching (NPQ) and cyclic electron transport (CEF)] and antioxidant systems both play important roles in protecting against abiotic factors in U. prolifera. (2) Cooperation between NPQ and CEF was observed in the ML group; CEF and the antioxidant system in the SL group work synergistically to protect the thalli. Furthermore, an inferred spatiotemporal attribute regarding the YSGT is presented: the significant changes in abiotic factors on the sea surface can easily affect the thalli of SL and ML from mid-June to mid-July, and those of LL can be affected in mid-July. This cooperation combined with the spatiotemporal attributes offers an explanation for the annual occurrence of the YSGT.HIGHLIGHTS    –Adaptive mechanisms of Ulva prolifera against abiotic factors.    –Cooperation between photosynthetic and antioxidant systems.    –Spatiotemporal attributes regarding the Yellow Sea green tide are presented

The use of selected bacteria and yeasts to control vibrio spp. in live food

Vibrio species are a significant causative of mass mortality in mariculture worldwide, which can quickly accumulate in live food and transmit into the larval gut. With restrictions on the use of antibiotics in aquaculture, finding a proper solution to reduce the risk of Vibriosis is vital. This study aimed to evaluate the susceptibility of Vibrio harveyi, V. campbellii, V. anguillarum, and V. parahaemolyticus to twenty-six bacterial and yeast strains and use the beneficial ones to enrich live food (Branchiopod, Artemia franciscana, rotifer, Brachionus plicatilis and copepod, Tigriopus japonicus). Thus, a modified disk diffusion method was applied. After a susceptibility assay, the bacteria and yeast beneficial in suppressing the Vibrio species were labeled by fluorescent stain and used to measure the accumulation potential in different live foods. Also, the beneficial bacteria and yeast were used to enrich live foods, and then the count of loaded Vibrio was estimated after 5, 10, 15, and 20 h by the serial dilution method. From the total bacteria and yeast strains that were used, Candida parapsilosis, Pseudoalteromonas flavipulchra, Lactobacillus sakei, Bacillus natto, and B. amyloliquefaciens inhibited all four Vibrio species. The results of microbial labeling showed that L. sakei in Artemia, C. parapsilosis in rotifers, and V. harveyi in copepods had the highest accumulation rate. The results of the estimation of loaded Vibrio in different live foods also showed that the use of beneficial bacteria and yeast each significantly reduced the count of Vibrio. Application of bacteria and yeast to suppress pathogenic Vibrio maybe a sustainable method for preventing this pathogen from harmfully invading aquaculture and may also aid in reducing the chances of antibiotic resistance in pathogenic Vibrio

Sex plays a role in the construction of epiphytic bacterial communities on the algal bodies and receptacles of Sargassum thunbergii

The community structures of epiphytic bacteria on the surface of macroalgae are closely related to their host algae, but there is a lack of research on the differences between the epiphytic bacterial communities of male and female algae and their reproductive tissues. In this study, high-throughput sequencing was used to compare epiphytic bacterial community structures on the intertidal macroalgae Sargassum thunbergii and their receptacles between male and female samples. The epiphytic bacteria on the male and female algal bodies and receptacles had similar community structures with a large number of shared bacteria, but the samples clearly clustered separately, and the abundances of dominant taxa, specific bacteria, and indicator species differed, indicating that epiphytic bacterial communities differed significantly between the male and female S. thunbergii and their receptacles. In addition, the abundance of many predicted functional genes was significantly different between epiphytic bacteria on male and female algal bodies and receptacles, especially metabolism-related genes, and the abundances of predicted functional genes of epiphytic bacteria were significantly higher on both types of male samples than on female samples. Our study confirmed that the sex of the host algae influenced the epiphytic bacterial community structures on algae and algal reproductive tissues, and this role was mainly related to the host metabolism. The results reveal the role of host plant sex in the formation of epiphytic bacterial communities. These findings are helpful for obtaining an in-depth understanding of the construction mechanism of algae-associated bacteria

Allelopathic effects of Ulva pertusa, Corallina pilulifera and Sargassum thunbergii on the growth of the dinoflagellates Heterosigma akashiwo and Alexandrium tamarense

The allelopathic effects of fresh tissue, dry powder and aqueous extracts of three macroalgae, Ulva pertusa, Corallina pilulifera and Sargassum thunbergii, on the growth of the dinoflagellates Heterosigma akashiwo and Alexandrium tamarense were evaluated using coexistence culture systems in which concentrations of the three macroalga were varied. The results of the coexistence assay showed that the growth of the two microalgae was strongly inhibited by using fresh tissue, dry powder and aqueous extracts of the three macroalga; the allelochemicals were lethal to H. akashiwo at relatively higher concentrations of the three macroalga. The macroalgae showing the most allelopathic effect on H. akashiwo and A. tamarense using fresh tissue were U. pertusa and S. thunbergii, using dry powder were S. thunbergii and U. pertusa, and using aqueous extracts were U. pertusa and C. pilulifera. We also examined the potential allelopathic effect on the two microalgae of culture filtrate of the three macroalga; culture medium filtrate initially exhibited no inhibitory effects when first added but inhibitory effects became apparent under semi-continuous addition, which suggested that continuous release of small quantities of rapidly degradable allelochemicals from the fresh macroalgal tissue were essential to effectively inhibit the growth of the two microalgae

Detection of Acylated Homoserine Lactone (AHL) in the Heterotrophic Bacteria Z-TG01 and Its Ecological Action on the Algae, Chlorella vulgaris

Heterotrophic bacteria Z-TG01 was isolated from the phycosphere of Chlorella vulgaris and identified as Sphingomonas paucimobilis by VITEK 2 Compact automated system with an excellent confidence level (99.0% probability). We detected acylated homoserine lactones (AHL) bioactivity in the growth process of Z-TG01 using Agrobacterium tumefaciens KYC55. The effects of C. vulgaris on AHL bioactivity, as well as the mutual influence of C. vulgaris and Z-TG01 in a co-culture system, were investigated. Results showed that AHL bioactivity of bacteria Z-TG01 varied with the bacteria density and was inhibited by supernatants of C. vulgaris culture in the early and middle exponential phases within 2 h (p<0.01), and in the late exponential phase within 1.5 h (p<0.05 or p<0.01). Within a certain cell density, bacteria Z-TG01 and C. vulgaris promote mutual growth in a co-culture system

Determination and contents analysis of negative ions in vegetable simultaneous by ion chromatography

A method of high-speed to determine some negative ions and their contents in vegetable by ion chromatography is proposed in this paper, which was based on the research of 2 negative ions in 16 kinds of vegetable from Hainan Danzhou market. This method is of easy usage, high-speed, good reappearance and the result is satisfactory. The correlation coefficients(r) of NO2- and NO3- were 0.9998 and 0.9991. Relative standard deviations (RSD) were 0.65% and 0.04%, respectively.By the determination of NO2-, and NO3- in vegetable, the results indicated that the contents of negative ions in different vegetables (the organ for eating) are fairly different

Liushou women’s happiness and its influencing factors in rural China

The economic development of urban cities in China has attracted a large number of labour from the rural countryside. The married migrant workers will usually leave their wives’ homes to look after the other family members and the farmland. A special term liushou women, has been created for this group of women. Among the 87 million rural residents, 47 million of them are liushou women according to the recent survey conducted by China Agricultural University. They play a crucial role in the development of rural economy and an essential role to the social stability of rural China. In this research, the factors that influence the happiness of liushou women were investigated in the Western part of China. Based on the population investigated, it was found that the financial situation, personality, government efficiency, conjugal relationship and relationship with in-laws are the significant factors influencing the happiness of liushou women. This finding demonstrates that the Chinese women are willing to sacrifice their personal interest for the interests of their families