Microcystis aeruginosa/Pseudomonas pseudoalcaligenes interaction effects on off-flavors in algae/bacteria co-culture system under different temperatures

Imaging mass spectrometry of interspecies metabolic exchange revealed the allelopathic interaction between Microcystis aeruginosa and its antagonist

The frequent outbreaks of cyanobacterial blooms which caused serious societal and economic loss have become a worldwide problem. Interactions between toxic cyanobacteria and heterotrophic bacteria competitors play a pivotal role in the formation of toxic cyanobacterial bloom, but the underlying mechanisms of interactions between them await further research. The antagonist activity of Pseudomonas grimontii (P.grimontii) was confirmed by reduction in chlorophyll a concentration of Microcystis aeruginosa (M. aeruginosa) in an infected culture for a 7d period. The initial concentration of P.grimontii affected the M. aeruginosa activity significantly. When the 10% (V/V) concentration of P.grimontii A01 and P.grimontii A14 cultures were infected, the reduction of M. aeruginosa reached to 91.81% and 78.25% after 7 days, respectively. While a 0.1% (v/v) concentration of P.grimontii A01 and P.grimontii A14 cultures were infected, the M. aeruginosa increased 31.13% and 16.67% occurred, respectively. The content of reactive oxygen species (ROS) and malondialdehyde (MDA) increased with increasing of P.grimontii fermentation liquid, indicating the M. aeruginosa underwent oxidative stress. Using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) imaging mass spectrometry (IMS) profiling of co-cultures of M. aeruginosa and its antagonist P.grimontii, we revealed novel interspecies allelopathic interactions and compete molecule. We showed the spatial secondary metabolites may mediate the interactions in which P.grimontii inhibits growth of M. aeruginosa. Additionally, we revealed how M. aeruginosa feedback to the P.grimontii, which stimulates secondary metabolites such as [D-Asp3]-microcystin-LR released by M. aeruginosa. IMS method highlights the significance of allelopathic interactions between a widely distributed toxic cyanobacteria and its bacteria competitors.

Interspecific competition between Microcystis aeruginosa and Pseudanadaena and their production of T&O compounds

Microcystis aeruginosa and Pseudanabaena are two common cyanobacterial species/genus and they can occur coincidently in many eutrophic lakes globally. These two cyanobacteria could produce Taste & Odor (T&O) compounds, and their production of T&O compounds might be changed when they are present coincidently. The amounts of T&O compounds and their producers may influence the effectiveness of water treatment processes. Therefore, the mutual interactions between Microcystis aeruginosa (FACHB-905, M) and Pseudanabaena sp. (FACHB-1277, P) on T&O compounds in co-cultures were evaluated in this study. Different initial cell concentrations of M and P, with ratios of M:P = 1:1, M:P = 1:2 and M:P = 2:1 were applied in the co-cultures. The growth of M was enhanced under all of the cyanobacterial cell ratios. The growth of P was enhanced under the ratio of M:P = 1:1, while it was inhibited under the ratios of M:P = 1:2 and M: P = 2:1. In addition, the growth of the two cyanobacteria and their production of β-cyclocitral and 2-methylisoborneol (2-MIB) in the filtrate of P were higher than those in the filtrate of M, which may be attributed to their associated secondary metabolites. The cell integrity and photosynthetic capacity of the two studied cyanobacteria are greatly affected by exposure to β-cyclocitral and 2-MIB. The results showed that β-cyclocitral and 2-MIB had the allelopathic effects on the two cyanobacteria species which might influence the composition of co-existing cyanobacteria and their production of T&O compounds.

Algae-Derived Bioactive Compounds with Anti-Lung Cancer Potential

Lung cancer is one of the major causes of death worldwide. Natural molecules with anti-lung cancer potential are of a great interest and considered as very promising alternative to substitute or enhance the efficiency of the conventional drugs. Recently, algae as source of high value-added compounds are considered as very promising source of these bioactive molecules. These are secondary metabolites that consist mainly of derivatives of peptides, carbohydrates, and lipids with various structures. Accordingly, various mechanisms by which different algae molecules demonstrate attenuation of tumor angiogenesis were stated and discussed. The mode of action of the algae bioactives is closely related to their nature and chemical structure. Furthermore, this literature review considers the synergistic effect between microalgae bioactives and conventional drugs and discuss the economic feasibility of producing microalgae bioactives at large scale to conclude with some future perspectives related to algae-based drug discovery.

Cyanobacteria derived taste and odor characteristics in various lakes in China: Songhua Lake, Chaohu Lake and Taihu Lake

In recent years, increasing eutrophication in large freshwater lakes, which are an important drinking water source for cities in China, have been resulted in substantial cyanobacteria blooms that could cause serious taste and odor (T&O) problems. In this investigation, three typical lakes (Songhua Lake, Chaohu Lake and Taihu Lake) as drinking water sources located in different geographical areas in China, were selected to study the problems of cyanobacteria-derived T&O (i.e., 2-methylisobornoel, geosmin, β-ionone, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, and 2-methylbenzofuran). The occurrence of T&O in target lakes was compared across various nutrition states and geographic locations, to get more information for early warning for algal bloom and T&O occurrence, being useful lake water management and purification. Results show that the occurrence of T&O in Songhua Lake was the poorest for the lowest nutrient state, as a first report in T&O research field in China. This is a lake located in Northeast China at high latitude, with lower water temperatures. The occurrence of T&O in Chaohu Lake was ranked in the middle. That in Taihu Lake was the most intensive. Finally, the relationship between water quality, T&O and its origin was analyzed by multivariate statistical methods (correlation analysis, principal component, and cluster analyses).

Living apart together-bacterial volatiles influence methanotrophic growth and activity

Volatile organic compounds play an important role in microbial interactions. However, little is known about how volatile-mediated interactions modulate biogeochemical processes. In this study, we show the effect of volatile-mediated interaction on growth and functioning of aerobic methane-oxidizing bacteria, grown in co-culture with five different heterotrophs. Both growth and methane oxidation of Methylobacter luteus were stimulated by interaction with specific heterotrophs. In Methylocystis parvus, we observed significant growth promotion, while methane oxidation was inhibited. Volatolomics of the interaction of each of the methanotrophs with Pseudomonas mandelii, revealed presence of a complex blend of volatiles, including dimethylsulfide, dimethyldisulfide, and bicyclic sesquiterpenes. Although the ecological role of the detected compounds remains to be elucidated, our results provide unprecedented insights into interspecific relations and associated volatiles for stimulating methanotroph functioning, which is of substantial environmental and biotechnological significance.

Occurrence of earthy–musty taste and odors in the Taihu Lake, China: spatial and seasonal patterns

The occurrence of earthy–musty T&O in the Taihu Lake evaluated in 2009/2010 and the main contributors are β-ionone, β-cyclocitral, IPMP and IBMP.