How do freshwater microalgae and cyanobacteria respond to antibiotics?

Antibiotic pollution is an emerging environmental challenge. Residual antibiotics from various sources, including municipal and industrial wastewater, sewage discharges, and agricultural runoff, are continuously released into freshwater environments, turning them into reservoirs that contribute to the development and spread of antibiotic resistance. Thus, it is essential to understand the impacts of antibiotic residues on aquatic organisms, especially microalgae and cyanobacteria, due to their crucial roles as primary producers in the ecosystem. This review summarizes the effects of antibiotics on major biological processes in freshwater microalgae and cyanobacteria, including photosynthesis, oxidative stress, and the metabolism of macromolecules. Their adaptive mechanisms to antibiotics exposure, such as biodegradation, bioadsorption, and bioaccumulation, are also discussed. Moreover, this review highlights the important factors affecting the antibiotic removal pathways by these organisms, which will promote the use of microalgae-based technology for the removal of antibiotics. Finally, we offer some perspectives on the opportunities for further studies and applications.

Gross Negligence: Impacts of Microplastics and Plastic Leachates on Phytoplankton Community and Ecosystem Dynamics.

Plastic debris is an established environmental menace affecting aquatic systems globally. Recently, microplastics (MP) and plastic leachates (PL) have been detected in vital human organs, the vascular system, and in vitro animal studies positing severe health hazards. MP and PL have been found in every conceivable aquatic ecosystem─from open oceans and deep sea floors to supposedly pristine glacier lakes and snow covered mountain catchment sites. Many studies have documented the MP and PL impacts on a variety of aquatic organisms, whereby some exclusively focus on aquatic microorganisms. Yet, the specific MP and PL impacts on primary producers have not been systematically analyzed. Therefore, this review focuses on the threats posed by MP, PL, and associated chemicals on phytoplankton, their comprehensive impacts at organismal, community, and ecosystem scales, and their endogenous amelioration. Studies on MP- and PL-impacted individual phytoplankton species reveal the production of reactive oxygen species, lipid peroxidation, physical damage of thylakoids, and other physiological and metabolic changes, followed by homo- and heteroaggregations, ultimately eventuating in decreased photosynthesis and primary productivity. Likewise, analyses of the microbial community in the plastisphere show a radically different profile compared to the surrounding planktonic diversity. The plastisphere also enriches multidrug-resistant bacteria, cyanotoxins, and pollutants, accelerating microbial succession, changing the microbiome, and thus, affecting phytoplankton diversity and evolution. These impacts on cellular and community scales manifest in changed ecosystem dynamics with widespread bottom-up and top-down effects on aquatic biodiversity and food web interactions. These adverse effects─through altered nutrient cycling─have "knock-on" impacts on biogeochemical cycles and greenhouse gases. Consequently, these impacts affect provisioning and regulating ecosystem services. Our citation network analyses (CNA) further demonstrate dire effects of MP and PL on all trophic levels, thereby unsettling ecosystem stability and services. CNA points to several emerging nodes indicating combined toxicity of MP, PL, and their associated hazards on phytoplankton. Taken together, our study shows that ecotoxicity of plastic particles and their leachates have placed primary producers and some aquatic ecosystems in peril.

7S,15R-Dihydroxy-16S,17S-epoxy-docosapentaenoic Acid Overcomes Chemoresistance of 5-Fluorouracil by Suppressing the Infiltration of Tumor-Associated Macrophages and Inhibiting the Activation of Cancer Stem Cells in a Colorectal Cancer Xenograft Model.

Although the tumor bulk is initially reduced by 5-fluorouracil (5-FU), chemoresistance developed due to prolonged chemotherapy in colorectal cancer (CRC). The enrichment of cancer stem cells (CSCs) and the infiltration of tumor-associated macrophages (TAMs) contribute to chemoresistance and poor outcomes. A docosahexaenoic acid derivative developed by our group, 7S,15R-dihydroxy-16S,17S-epoxy-docosapentaenoic acid (diHEP-DPA), exerts antitumor effects against TAMs infiltration and CSCs enrichment in our previous study. The current study aimed to investigate whether diHEP-DPA was able to overcome chemoresistance to 5-FU in CRCs, together with the potential synergistic mechanisms in a CT26-BALB/c mouse model. Our results suggested that although 5-FU inhibited tumor growth, 5-FU enriched CSCs via the WNT/ß-catenin signaling pathway, resulting in chemoresistance in CRCs. However, we revealed that 5-FU promoted the infiltration of TAMs via the NF-kB signaling pathway and improved epithelial-mesenchymal transition (EMT) via the signal transducer and activator of the transcription 3 (STAT3) signaling pathway; these traits were believed to contribute to CSC activation. Furthermore, supplementation with diHEP-DPA could overcome drug resistance by decreasing the CSCs, suppressing the infiltration of TAMs, and inhibiting EMT progression. Additionally, the combinatorial treatment of diHEP-DPA and 5-FU effectively enhanced phagocytosis by blocking the CD47/signal regulatory protein alpha (SIRPα) axis. These findings present that diHEP-DPA is a potential therapeutic supplement to improve drug outcomes and suppress chemoresistance associated with the current 5-FU-based therapies for colorectal cancer.

The emerging potential of natural and synthetic algae-based microbiomes for heavy metal removal and recovery from wastewaters.

Heavy Metal (HM) bioremoval by microbes is a successful, environment-friendly technique, particularly at low concentrations of HMs. Studies using algae, bacteria, and fungi reveal promising capabilities in isolation and when used in consortia. Yet, few reviews have emphasized individual and collective HM removal rates and the associated mechanisms in natural or synthetic microbiomes. Besides discussing the limitations of conventional and synthetic biology approaches, this review underscores the utility of indigenous microbial taxon, i.e., algae, fungi, and bacteria, in HM removal with adsorption capacities and their synergistic role in microbiome-led studies. The detoxification mechanisms studied for certain HMs indicate distinctive removal pathways in each taxon which points to an enhanced effect when used as a microbiome. The role and higher efficacies of the designer microbiomes with complementing and mutualistic taxa are also considered, followed by recovery options for a circular bioeconomy. The citation network analysis further validates the multi-metal removal ability of microbiomes and the restricted capabilities of the individual counterparts. In precis, the study reemphasizes increased metal removal efficiencies of inter-taxon microbiomes and the mechanisms for synergistic and improved removal, eventually drawing attention to the benefits of ecological engineering approaches compared to other alternatives.

Development of a novel nannochloropsis strain with enhanced violaxanthin yield for large-scale production.

BACKGROUND: Nannochloropsis is a marine microalga that has been extensively studied. The major carotenoid produced by this group of microalgae is violaxanthin, which exhibits anti-inflammatory, anti-photoaging, and antiproliferative activities. Therefore, it has a wide range of potential applications. However, large-scale production of this pigment has not been much studied, thereby limiting its industrial application. RESULTS: To develop a novel strain producing high amount of violaxanthin, various Nannochloropsis species were isolated from seawater samples and their violaxanthin production potential were compared. Of the strains tested, N. oceanica WS-1 exhibited the highest violaxanthin productivity; to further enhance the violaxanthin yield of WS-1, we performed gamma-ray-mediated random mutagenesis followed by colorimetric screening. As a result, Mutant M1 was selected because of its significant higher violaxanthin content and biomass productivity than WS-1 (5.21 ± 0.33 mg g- 1 and 0.2101 g L- 1 d- 1, respectively). Subsequently, we employed a 10 L-scale bioreactor to confirm the large-scale production potential of M1, and the results indicated a 43.54 % increase in violaxanthin production compared with WS-1. In addition, comparative transcriptomic analysis performed under normal light condition identified possible mechanisms associated with remediating photo-inhibitory damage and other key responses in M1, which seemed to at least partially explain enhanced violaxanthin content and delayed growth. CONCLUSIONS: Nannochloropsis oceanica mutant (M1) with enhanced violaxanthin content was developed and its physiological characteristics were investigated. In addition, enhanced production of violaxanthin was demonstrated in the large-scale cultivation. Key transcriptomic responses that are seemingly associated with different physiological responses of M1 were elucidated under normal light condition, the details of which would guide ongoing efforts to further maximize the industrial potential of violaxanthin producing strains.

Functional expression of polyethylene terephthalate-degrading enzyme (PETase) in green microalgae.

BACKGROUND: For decades, plastic has been a valuable global product due to its convenience and low price. For example, polyethylene terephthalate (PET) was one of the most popular materials for disposable bottles due to its beneficial properties, namely impact resistance, high clarity, and light weight. Increasing demand of plastic resulted in indiscriminate disposal by consumers, causing severe accumulation of plastic wastes. Because of this, scientists have made great efforts to find a way to biologically treat plastic wastes. As a result, a novel plastic degradation enzyme, PETase, which can hydrolyze PET, was discovered in Ideonella sakaiensis 201-F6 in 2016. RESULTS: A green algae, Chlamydomonas reinhardtii, which produces PETase, was developed for this study. Two representative strains (C. reinhardtii CC-124 and CC-503) were examined, and we found that CC-124 could express PETase well. To verify the catalytic activity of PETase produced by C. reinhardtii, cell lysate of the transformant and PET samples were co-incubated at 30 °C for up to 4 weeks. After incubation, terephthalic acid (TPA), i.e. the fully-degraded form of PET, was detected by high performance liquid chromatography analysis. Additionally, morphological changes, such as holes and dents on the surface of PET film, were observed using scanning electron microscopy. CONCLUSIONS: A PET hydrolyzing enzyme, PETase, was successfully expressed in C. reinhardtii, and its catalytic activity was demonstrated. To the best of our knowledge, this is the first case of PETase expression in green algae.

The Ancient Phosphatidylinositol 3-Kinase Signaling System Is a Master Regulator of Energy and Carbon Metabolism in Algae.

Algae undergo a complete metabolic transformation under stress by arresting cell growth, inducing autophagy and hyper-accumulating biofuel precursors such as triacylglycerols and starch. However, the regulatory mechanisms behind this stress-induced transformation are still unclear. Here, we use biochemical, mutational, and "omics" approaches to demonstrate that PI3K signaling mediates the homeostasis of energy molecules and influences carbon metabolism in algae. In Chlamydomonas reinhardtii, the inhibition and knockdown (KD) of algal class III PI3K led to significantly decreased cell growth, altered cell morphology, and higher lipid and starch contents. Lipid profiling of wild-type and PI3K KD lines showed significantly reduced membrane lipid breakdown under nitrogen starvation (-N) in the KD. RNA-seq and network analyses showed that under -N conditions, the KD line carried out lipogenesis rather than lipid hydrolysis by initiating de novo fatty acid biosynthesis, which was supported by tricarboxylic acid cycle down-regulation and via acetyl-CoA synthesis from glycolysis. Remarkably, autophagic responses did not have primacy over inositide signaling in algae, unlike in mammals and vascular plants. The mutant displayed a fundamental shift in intracellular energy flux, analogous to that in tumor cells. The high free fatty acid levels and reduced mitochondrial ATP generation led to decreased cell viability. These results indicate that the PI3K signal transduction pathway is the metabolic gatekeeper restraining biofuel yields, thus maintaining fitness and viability under stress in algae. This study demonstrates the existence of homeostasis between starch and lipid synthesis controlled by lipid signaling in algae and expands our understanding of such processes, with biotechnological and evolutionary implications.

Autophagic flux is required for the synthesis of triacylglycerols and ribosomal protein turnover in Chlamydomonas.

Autophagy is an intracellular catabolic process that allows cells to recycle unneeded or damaged material to maintain cellular homeostasis. This highly dynamic process is characterized by the formation of double-membrane vesicles called autophagosomes, which engulf and deliver the cargo to the vacuole. Flow of material through the autophagy pathway and its degradation in the vacuole is known as autophagic flux, and reflects the autophagic degradation activity. A number of assays have been developed to determine autophagic flux in yeasts, mammals, and plants, but it has not been examined yet in algae. Here we analyzed autophagic flux in the model green alga Chlamydomonas reinhardtii. By monitoring specific autophagy markers such as ATG8 lipidation and using immunofluorescence and electron microscopy techniques, we show that concanamycin A, a vacuolar ATPase inhibitor, blocks autophagic flux in Chlamydomonas. Our results revealed that vacuolar lytic function is needed for the synthesis of triacylglycerols and the formation of lipid bodies in nitrogen- or phosphate-starved cells. Moreover, we found that concanamycin A treatment prevented the degradation of ribosomal proteins RPS6 and RPL37 under nitrogen or phosphate deprivation. These results indicate that autophagy might play an important role in the regulation of lipid metabolism and the recycling of ribosomal proteins under nutrient limitation in Chlamydomonas.

Black Phosphorus (BP) Nanodots for Potential Biomedical Applications.

Recently, the appeal of 2D black phosphorus (BP) has been rising due to its unique optical and electronic properties with a tunable band gap (≈0.3-1.5 eV). While numerous research efforts have recently been devoted to nano- and optoelectronic applications of BP, no attention has been paid to promising medical applications. In this article, the preparation of BP-nanodots of a few nm to <20 nm with an average diameter of ≈10 nm and height of ≈8.7 nm is reported by a modified ultrasonication-assisted solution method. Stable formation of nontoxic phosphates and phosphonates from BP crystals with exposure in water or air is observed. As for the BP-nanodot crystals' stability (ionization and persistence of fluorescent intensity) in aqueous solution, after 10 d, ≈80% at 1.5 mg mL(-1) are degraded (i.e., ionized) in phosphate buffered saline. They showed no or little cytotoxic cell-viability effects in vitro involving blue- and green-fluorescence cell imaging. Thus, BP-nanodots can be considered a promising agent for drug delivery or cellular tracking systems.

Chelatococcus caeni sp. nov., isolated from a biofilm reactor sludge sample.

A polyphasic taxonomic study was carried out on strain EBR-4-1(T), which was isolated from a biofilm reactor in the Republic of Korea. The cells of the strain were Gram-stain-negative, non-spore-forming, motile and rod-shaped. Comparative 16S rRNA gene sequence studies showed a clear affiliation of this strain to the Alphaproteobacteria, and it was most closely related to Chelatococcus daeguensis CCUG 54519(T), Chelatococcus sambhunathii HT4(T), and Chelatococcus asaccharovorans DSM 6462(T) with 16S rRNA gene sequence similarities to the type strains of these species of 98.8 %, 98.7 %, and 96.3 %, respectively. The G+C content of the genomic DNA of strain EBR-4-1(T) was 68.7 mol%. Phenotypic and chemotaxonomic data [Q-10 as the major ubiquinone; C19 : 0cycloω8c, C18 : 1 2-OH, and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) as the major fatty acids] supported the affiliation of strain EBR-4-1(T) to the genus Chelatococcus. On the basis of the polyphasic evidence, it is proposed that strain EBR-4-1(T) should be assigned to a new species, Chelatococcus caeni sp. nov. The type strain is EBR-4-1(T) ( = KCTC 32487(T) = JCM 30181(T)).

Flaviflexus salsibiostraticola sp. nov., an actinobacterium isolated from a biofilm reactor.

A Gram-stain-positive, aerobic, non-motile, non-spore-forming, cocci-shaped actinobacterium, designated strain EBR4-1-2(T), was isolated from a biofilm reactor in Korea. Comparative 16S rRNA gene sequence studies showed the isolate was clearly affiliated with the class Actinobacteria, and was related most closely to Flaviflexus huanghaiensis H5(T), showing 98.9 % similarity. Cells of strain EBR4-1-2(T) formed yellow colonies on R2A agar, contained MK-9(H4) as the predominant menaquinone, and included C18 : 1ω9c, C16 : 0, C16 : 1ω9c and C14 : 0 as the major fatty acids. The cell-wall peptidoglycan type was A5α (l-Lys-l-Ala-l-Lys-d-Glu). The G+C content of the genomic DNA of strain EBR4-1-2(T) was 65.6 mol%. Thus, the combined genotypic and phenotypic data supported the conclusion that strain EBR4-1-2(T) represents a novel species of the genus Flaviflexus, for which the name Flaviflexus salsibiostraticola sp. nov. is proposed. The type strain is EBR4-1-2(T) ( = KCTC 33148(T) = JCM 19016(T)).

(M, N)-soft intersection BL-algebras and their congruences.

The purpose of this paper is to give a foundation for providing a new soft algebraic tool in considering many problems containing uncertainties. In order to provide these new soft algebraic structures, we discuss a new soft set-(M, N)-soft intersection set, which is a generalization of soft intersection sets. We introduce the concepts of (M, N)-SI filters of BL-algebras and establish some characterizations. Especially, (M, N)-soft congruences in BL-algebras are concerned.

The interaction between fuzzy subsets and groupoids.

We discuss properties of a class of real-valued functions on a set X (2) constructed as finite (real) linear combinations of functions denoted as [(X, ∗); µ ], where (X, ∗) is a groupoid (binary system) and µ is a fuzzy subset of X and where [(X, ∗); µ ](x, y): = µ (x ∗ y) - min{µ (x), µ (y)}. Many properties, for example, µ being a fuzzy subgroupoid of X, ∗), can be restated as some properties of [(X, ∗); µ]. Thus, the context provided opens up ways to consider well-known concepts in a new light, with new ways to prove known results as well as to provide new questions and new results. Among these are identifications of many subsemigroups and left ideals of (Bin(X), □) for example.

Ideal theory in semigroups based on intersectional soft sets.

The notions of int-soft semigroups and int-soft left (resp., right) ideals are introduced, and several properties are investigated. Using these notions and the notion of inclusive set, characterizations of subsemigroups and left (resp., right) ideals are considered. Using the notion of int-soft products, characterizations of int-soft semigroups and int-soft left (resp., right) ideals are discussed. We prove that the soft intersection of int-soft left (resp., right) ideals (resp., int-soft semigroups) is also int-soft left (resp., right) ideals (resp., int-soft semigroups). The concept of int-soft quasi-ideals is also introduced, and characterization of a regular semigroup is discussed.

(n - 1)-Step derivations on n-groupoids: the case n = 3.

We define a ranked trigroupoid as a natural followup on the idea of a ranked bigroupoid. We consider the idea of a derivation on such a trigroupoid as representing a two-step process on a pair of ranked bigroupoids where the mapping d is a self-derivation at each step. Following up on this idea we obtain several results and conclusions of interest. We also discuss the notion of a couplet (D, d) on X, consisting of a two-step derivation d and its square D = d ∘ d, for example, whose defining property leads to further observations on the underlying ranked trigroupoids also.

A new extended soft intersection set to (M, N)-SI implicative fitters of BL-algebras.

Molodtsov's soft set theory provides a general mathematical framework for dealing with uncertainty. The concepts of (M, N)-SI implicative (Boolean) filters of BL-algebras are introduced. Some good examples are explored. The relationships between (M, N)-SI filters and (M, N)-SI implicative filters are discussed. Some properties of (M, N)-SI implicative (Boolean) filters are investigated. In particular, we show that (M, N)-SI implicative filters and (M, N)-SI Boolean filters are equivalent.

Unlocking synergies: Harnessing the potential of biological methane sequestration through metabolic coupling between Methylomicrobium alcaliphilum 20Z and Chlorella sp. HS2.

A halotolerant consortium between microalgae and methanotrophic bacteria could effectively remediate in situ CH4 and CO2, particularly using saline wastewater sources. Herein, Methylomicrobium alcaliphilum 20Z was demonstrated to form a mutualistic association with Chlorella sp. HS2 at a salinity level above 3.0%. Co-culture significantly enhanced the growth of both microbes, independent of initial inoculum ratios. Additionally, increased methane provision in enclosed serum bottles led to saturated methane removal. Subsequent analyses suggested nearly an order of magnitude increase in the amount of carbon sequestered in biomass in methane-fed co-cultures, conditions that also maintained a suitable cultural pH suitable for methanotrophic growth. Collectively, these results suggest a robust metabolic coupling between the two microbes and the influence of the factors other than gaseous exchange on the assembled consortium. Therefore, multi-faceted investigations are needed to harness the significant methane removal potential of the identified halotolerant consortium under conditions relevant to real-world operation scenarios.

Caulobacter daechungensis sp. nov., a stalked bacterium isolated from a eutrophic reservoir.

A Gram-stain-negative, aerobic, non-spore-forming, curved, rod-shaped bacterium, H-E3-2(T), was isolated from a water sample taken from Daechung Reservoir, Republic of Korea, during the late-blooming period of cyanobacteria. Strain H-E3-2(T) was motile with a single polar flagellum or non-motile (stalked cell). Comparative 16S rRNA gene sequence studies showed the isolate had a clear affiliation with the class Alphaproteobacteria and was most closely related to Caulobacter fusiformis ATCC 15257(T) and Caulobacter mirabilis LMG 24261(T), showing 97.6 and 97.3 % 16S rRNA gene sequence similarity, respectively, and 95.3-96.3 % similarity to all other species of the genus Caulobacter. The predominant ubiquinone was Q-10. The major fatty acids were summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c) and C16 : 0. The G+C content of the genomic DNA of strain H-E3-2(T) was 64.7 mol%. DNA-DNA hybridization values of strain H-E3-2(T) with C. fusiformis ATCC 15257(T) and C. mirabilis LMG 24261(T) were 21.2 and 19.7 %, respectively. Thus, based on the results of polyphasic analysis, it is proposed that strain H-E3-2(T) represents a novel species of the genus Caulobacter, for which the name Caulobacter daechungensis sp. nov. is proposed. The type strain is H-E3-2(T) ( = KCTC 32211(T) = JCM 18689(T)).

Geodermatophilus soli sp. nov. and Geodermatophilus terrae sp. nov., two actinobacteria isolated from grass soil.

Two strains, PB34(T) and PB261(T), were isolated from grass soil sampled in Daejeon, Republic of Korea. Comparative 16S rRNA gene sequence studies showed the two bacteria to be clearly affiliated with the phylum Actinobacteria and most closely related to the genus Geodermatophilus, showing 16S rRNA gene sequence similarities to the type strains of species of the genus Geodermatophilus of 95.0-96.3 % and sharing 98.5 % similarity between the two strains. The two strains were Gram-stain-positive, aerobic, motile and rod-shaped bacteria. The peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. The predominant menaquinones were MK-9(H4) and MK-9(H0). The major fatty acids were iso-C15 : 0, iso-C16 : 0, iso-C17 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) for strain PB34(T) and iso-C14 : 0, iso-C15 : 0, iso-C16 : 0 and C16 : 0 for strain PB261(T). The G+C contents of the genomic DNA of strains PB34(T) and PB261(T) were 73.2 mol% and 74.1 mol%, respectively. Thus, based on the evidence of a polyphasic study, it is proposed that strains PB34(T) and PB261(T) represent two novel species, for which the names Geodermatophilus soli sp. nov. (type strain PB34(T) = KCTC 19880(T) = JCM 17785(T)) and Geodermatophilus terrae sp. nov. (type strain PB261(T) = KCTC 19881(T) = JCM 17786(T)) are proposed.

Amnibacterium soli sp. nov., an actinobacterium isolated from grass soil.

A Gram-stain-positive, aerobic, non-motile, non-spore-forming, short rod-shaped actinobacterium, designated strain PB243(T), was isolated from grass soil sampled in Daejeon, Republic of Korea. Comparative 16S rRNA gene sequence studies showed the isolate was clearly affiliated with the class Actinobacteria, and most closely related to Amnibacterium kyonggiense KEMC 51201-037(T), showing 98.8 % 16S rRNA gene sequence similarity. Cells of strain PB243(T) formed yellow colonies on R2A agar, contained MK-11 and MK-12 as the predominant menaquinones, l-2,4-diaminobutyric acid as the diagnostic cell-wall diamino acid, and anteiso-C15:0 and iso-C16:0 among the major fatty acids. The acyl type of the muramic acid was acetyl. The G+C content of the genomic DNA of strain PB243(T) was 71.5 mol%. Thus, the combined genotypic and phenotypic data supported the conclusion that strain PB243(T) represents a novel species of the genus Amnibacterium, for which the name Amnibacterium soli sp. nov. is proposed. The type strain is PB243(T) ( = KCTC 33147(T) = JCM 19015(T)).