Cells Ml-1 Research Articles

Microbial distribution in Mudbank regions off Alappuzha, South-West coast of India.

The coastal waters of Kerala, in the South Eastern Arabian Sea (SEAS), are unique during the Southwest monsoon season due to the concurrent occurrence of two physical processes, the upwelling and Mudbanks. However, little is known about the viral ecology and activity in a system where upwelling and Mudbanks coexist, though it is generally recognized that microbial assemblages play a vital role in the food web dynamics of marine systems, particularly in upwelling. Water samples were taken from monsoon and pre-monsoon period from three locations, (M1, M2, and M3) off Alappuzha, on the southwest coast of India to examine the viral activity and distribution. The dissolved oxygen levels showed the incursion of hypoxic waters in all the stations during the peak upwelling period. Upwelling signals were prominent in all the stations, but Mudbank and upwelling co-occurred at M2 alone during monsoon. The abundance of viruses ranged from 0.86 to 15.68 × 106 Viral-like Particles (VLPs mL-1) and prokaryotic abundance ranged from 2.73-16.26 × 105 cells mL-1. Viral and prokaryotic abundance was significantly higher in the monsoon compared to pre and late-monsoon. Based on Transmission electron microscopy (TEM) results, the non-tailed viruses constituted the major (43%) proportion of the total viruses in this study region. However, the viral production rates and viral-mediated bacterial mortality were high in the pre-monsoon compared to the monsoon and late-monsoon periods. There was no obvious effect of Mudbanks on viral dynamics and the observed variations in virological and hydrological features were governed mainly by coastal upwelling.

Objective: To investigate the use of biological ensiling of organic residues generated by pectiniculture as a nutritive medium in the production of the microalgae Tetraselmis suecica. Theoretical Framework: Biological ensiling is a process that transforms organic residues into a nutritive source through fermentation. In this context, pectiniculture residues, specifically the soft parts of fan shells, can be recycled and used

Objective: To investigate the use of biological ensiling of organic residues generated by pectiniculture as a nutritive medium in the production of the microalgae Tetraselmis suecica. Theoretical Framework: Biological ensiling is a process that transforms organic residues into a nutritive source through fermentation. In this context, pectiniculture residues, specifically the soft parts of fan shells, can be recycled and used as alternative media. Microalgae, such as T. suecica, are photosynthetic organisms that require nutrients for their growth, and their cultivation can benefit from these residues. Method: Twelve vertical bioreactors were used with three experimental treatments (T1, T2, T3) and treatments, one control (CT), with three replicates per treatment. The microalgae were inoculated at a density of 70 x 104 cells mL-1 in a culture volume of 80 L. Cultures were grown in open air with constant aeration. 0-, 60-, 70-, and 80-mL L-1 of the biological silage of fan shell soft parts (EBCA) were dosed. The silage was also chemically characterized and the growth of the microalgae and its relationship with temperature, salinity and pH were determined. Results and Discussion: The results showed that the dosage of 70 mL L-1 of EBCA in T. suecica cultures favors the growth of the microalgae. A significant increase in biomass and cell density was observed compared to the other treatments, indicating that this concentration of silage provides a suitable nutrient medium. The study also analyzed how temperature, salinity and pH conditions affect the growth of T. suecica, finding that certain optimal ranges of these factors can maximize biomass production. Research Implications: Our study demonstrates that pectin culture waste can be effectively recycled as a culture medium for T. suecica production, offering a sustainable and environmentally friendly solution for waste management. This could reduce reliance on traditional culture media and promote more sustainable practices in aquaculture and the microalgal industry. Originality/Value: This study stands out for its innovative approach in the use of organic waste from pectiniculture, such as the soft parts of the fan shell, for the generation of an alternative nutrient medium for microalgae. In addition, large volumes of fan shell wastes are currently being generated, so our work contributes to the management of these wastes.

Nanozyme-Based Pump-free Microfluidic Chip for Colorectal Cancer Diagnosis via Circulating Cancer Stem Cell Detection.

Circulating cancer stem cells (CCSCs) are subpopulations of cancer cells with high tumorigenicity, chemoresistance, and metastatic potential, which are also major drivers of disease progression. Herein, to achieve the prediction of tumor diagnosis and progression in colorectal cancer (CRC), a new, automated, and portable lateral displacement patterned pump-free (LP) microfluidic chip (LP-chip) with the CoPt3 nanozyme was established for CCSC capture and detection in peripheral blood and feces samples ex vivo. In this design, CoPt3@HA probes with functions of magnetic separation and colorimetric signal transduction by peroxidase-mimicking activity were applied for the capture of CCSCs and signal output in clinical samples. The generated colors of polydopamine (PDA) were quantifiable through the smartphone APP and visualizable by the naked eye in the test line (T line) and control line (C line) of the LP-chip. In the optimal experimental conditions, the CCSC concentration was sensitive to change in the range 0-105 cells mL-1, with a detection limit of 3 cells mL-1 (S/N = 3). Preliminary studies of clinical samples suggest that the platform has the potential for prediction of colorectal cancer progression and poor prognosis. Overall, the LP-chip provides potential strategies for timely diagnosis, therapeutic monitoring, and recurrence prediction to improve home-based patient care.

Volcanic ash in the water column: Cellular, physiological and anatomical implications for the gastropod suspension-feeder Crepipatella peruviana (Lamarck, 1822)

The influx of volcanic ash into seawater alters particle composition with implications for the cellular, physiological and anatomical response of suspension-feeding organisms. Adult females of Crepipatella peruviana were exposed to three diets consisting of a fixed concentration of 50,000 cells ml−1 of the microalga Isochrysis galbana plus different concentrations of ash particles (30, 90 and 150 mg L−1). The objective was to determine the cellular, physiological and anatomical responses. Mortality increased with ash concentrations, while feeding and respiration rates, tissue weight, and condition index decreased. The gills showed severe degradation of cilia and the presence of large mucous aggregates of cilia and ash. An increase in ash resulted in decreased lipid peroxidation and protein carbonyls, but increased total antioxidant capacity and phenols. Thus, volcanic ash particles may exert a high impact at both cellular and physiological levels for C. peruviana, where inhibition of gill function reduces the ability to acquire food.

Effect of diet on larval settlement, growth, and spat survival of the oyster Crassostrea gigas (Thunberg, 1793)

This study aimed to assess the impact of microalgal concentrations in diets on the settlement and metamorphosis stages of pediveliger larvae and spat of Crassostrea gigas oysters. Diets containing microalgal concentrations of 8, 12, and 16×104 cells mL-1 were administered for seven days during the larval settlement phase of pediveliger larvae. In the metamorphosis and postlarval cultivation phases, diets with microalgal concentrations of 8, 16, 24, and 32×104 cells mL-1 and a control group without food were tested for 14 and 21 days, respectively. Growth, yield, and survival were assessed every seven days. The diet comprised 30% Isochrysis galbana and 70% Chaetoceros muelleri microalgae. In the metamorphosis phase, the results revealed no significant differences in larval metamorphosis rate and survival across the tested diets. The concentrations exhibited similar survival in the spat with an initial average shell height of 0.657 ± 0.05 mm, with a significant difference only in growth. In the spat with an initial average shell height of 0.830 ± 0.12 mm, no differences in survival were observed among the tested concentrations. We concluded that diets of 12 and 16×104 cells mL-1 provide high rates of larval metamorphosis and spat yield during the larval settlement and metamorphosis phases. During the spat cultivation phases, diets of 32 and 24×104 cells mL-1 could optimize the cultivation time and yield of C. gigas spat in the laboratory. However, when considering survival alone, no advantage was found in providing a diet with a microalgal concentration above 8×104 cells mL-1 across all C. gigas oyster cultivation phases.

Somatic cell count as an indicator of subclinical mastitis and increased inflammatory response in asymptomatic lactating women.

This pilot study suggests that SCC at a level of (greater than or equal to) 250,000 cells mL-1, as used in the dairy industry, is a suitable index to identify asymptomatic subclinical mastitis in lactating women since it reflects a significant increase in the inflammatory response compared to milk samples from healthy women. Using this index should aid studies into the short- and long-term consequences of subclinical mastitis for mother and infant.

Investigating the role of allelochemicals in the interaction between Alexandrium monilatum and other phytoplankton species

Species of the dinoflagellate genus Alexandrium can release bioactive extracellular compounds with allelopathic effects (e.g., immobilization, inhibition of growth, photosynthesis or lysis) towards other phytoplanktonic organisms. In the lower Chesapeake Bay, Virginia, US, succession or co-occurrence of blooms of Akashiwo sanguinea, Margalefidinium polykrikoides and the goniodomin-producing A. monilatum tend to be common during summer months, however the allelopathic potential of A. monilatum, and how it may affect bloom dynamics, has not be studied. We used a rapid fluorescence-based bioassay as well as flow cytometry and an assessment of immobilization to determine the potential effects of A. monilatum culture supernatants on M. polykrikoides, A. sanguinea and the diatom Chaetoceros muelleri (included as a reference strain). In addition, we also investigated the effects of standards of known A. monilatum toxins goniodomin A (GDA) and GDA seco-acid (GDA-sa). Exposure of C. muelleri to culture supernatants from two different strains of A. monilatum resulted in an inhibition of the maximum quantum yield of the photosystem II (Fv/Fm) and cell lysis of the diatom, with strain-specific variation observed, highlighted by a 30-fold difference in the effective concentration resulting in 10 % inhibition (EC10) and 2-fold difference in the lethal concentration resulting in 50 % mortality (LC50) between the two A. monilatum strains tested. Exposure of M. polykrikoides to A. monilatum culture supernatants resulted in a decrease in motility (at ≥ 500 eq. cells mL-1) along with a decrease in Fv/Fm (at ≥ 1,500 cells mL-1) and altered cellular morphology (at ≥ 3,500 eq. cells mL-1). No effect was observed when A. sanguinea was exposed to A. monilatum culture supernatants (at the concentrations tested in these studies). When M. polykrikoides was exposed to the GDA standard, its Fv/Fm (at ≥ 1,951 nM) and motility (at ≥ 390 nM) decreased, and its morphology (at ≥ 975 nM) was modified. The study of supernatant time- and temperature-stability, and the absence of a relationship between observed effects and goniodomin concentrations suggested the presence of additional unknown allelochemicals distinct from goniodomins, as has been observed for other Alexandrium species. Immobilization of M. polykrikoides by A. monilatum culture supernatants and GDA standard in laboratory-based exposure experiments may indicate that A. monilatum has a competitive advantage when both species co-occur in the Chesapeake Bay and this warrants further testing.

Continuous and Intermittent Exposure to the Toxigenic Cyanobacterium Microcystis aeruginosa Differentially Affects the Survival and Reproduction of Daphnia curvirostris.

Anthropic eutrophication leads to water quality degradation because it may cause the development of harmful cyanobacterial blooms, affecting aquatic biota and threatening human health. Because in the natural environment zooplankters are exposed continuously or intermittently to cyanotoxins in the water or through cyanobacterial consumption, this study aimed to assess the effects of the toxigenic Microcystis aeruginosa VU-5 by different ways of exposure in Daphnia curvirostris. The acute toxicity produced by the cells, the aqueous crude extract of cells (ACE), and the cell-free culture medium (CFM) were determined. The effect on the survival and reproduction of D. curvirostris under continuous and intermittent exposure was determined during 26 d. The LC50 was 407,000 cells mL-1; exposure to the ACE and CFM produced mortality lower than 20%. Daphnia survivorship and reproduction were significantly reduced. Continuous exposure to Microcystis cells caused 100% mortality on the fourth day. Exposure during 4 and 24 h in 48 h cycles produced adult mortality, and reproduction decreased as the exposure time and the Microcystis concentrations increased. The higher toxicity of cells than the ACE could mean that the toxin's absorption is higher in the digestive tract. The temporary exposure to Microcystis cells produced irreversible damage despite the recovery periods with microalgae as food. The form and the continuity in exposure to Microcystis produced adverse effects, warning about threats to the zooplankton during HCBs.

Fabrication of Aluminum Foil Integrated Pegylated Gold Nanoparticle Surface-Enhanced Raman Scattering Substrate for the Detection and Classification of Uropathogenic Bacteria.

Rapid detection and classification of pathogenic microbes for food hygiene, healthcare, environmental contamination, and chemical and biological exposures remain a major challenge due to nonavailability of fast and accurate detection methods. The delay in clinical diagnosis of the most frequent bacterial infections, particularly urinary tract infections (UTIs), which affect about half of the population at least once in their lifetime, can be fatal if not detected and treated appropriately. In this work, we have fabricated aluminum (Al) foil integrated pegylated gold nanoparticles (AuNPs) as a potential surface-enhanced Raman scattering (SERS) substrate, which is used for the detection and classification of uropathogens, namely, E. coli, S. aureus, and P. aeruginosa directly from the culture without any pretreatment. The substrate is first drop cast with bacterial pellets and then pegylated AuNPs, and the interaction of two on Al foil base gives identifiable characteristic Raman peaks with good reproducibility. With the use of chemometric methods such as principal component analysis (PCA), the Al foil-based SERS substrate offers a quick, effective detection and classification of three strains of UTI bacteria with the least bacterial concentration (105 cells mL-1) necessary for clinical diagnosis. In addition, this substrate was able to detect E. coli positive clinical samples by giving SERS fingerprint information directly from centrifuged urine samples within minutes. The stability of pegylated AuNPs provides for its application at the point of care with rapid and easy detection of uropathogens as well as the possibility of advancement in healthcare applications.

High infectivity and waterborne transmission of seagrass wasting disease.

Pathogen transmission pathways are fundamental to understanding the epidemiology of infectious diseases yet are challenging to estimate in nature, particularly in the ocean. Seagrass wasting disease (SWD), caused by Labyrinthula zosterae, impacts seagrass beds worldwide and is thought to be a contributing factor to declines; however, little is known about natural transmission of SWD. In this study, we used field and laboratory experiments to test SWD transmission pathways and temperature sensitivity. To test transmission modes in nature, we conducted three field experiments out-planting sentinel Zostera marina shoots within and adjacent to natural Z. marina beds (20 ± 5 and 110 ± 5 m from bed edge). Infection rates and severity did not differ among outplant locations, implicating waterborne transmission. The infectious dose of L. zosterae through waterborne exposure was assessed in a controlled laboratory experiment. The dose to 50% disease was 6 cells ml-1 and did not differ with the temperatures tested (7.5°C and 15°C). Our results show L. zosterae is transmissible through water without direct contact with infected plants. Understanding the transmission dynamics of this disease in the context of changing ocean conditions will improve Z. marina protection and restoration in critical coastal habitats worldwide.

Life history traits of the gastropod-associated bacterivorous nematode Caenorhabditis brenneri (Nematoda: Rhabditida)

Abstract. Dalan L, Tañan V, Diano MA, Demayo C, Tabelin M, Sumaya NH. 2024. Life history traits of the gastropod-associated bacterivorous nematode Caenorhabditis brenneri (Nematoda: Rhabditida). Biodiversitas 25: 3106-3113. Caenorhabditis species are associated with decaying plant materials and invertebrates such as terrestrial gastropods. Few Caenorhabditis species have been studied regarding their ecology, genetics, development, and essential life history traits (LHT). In this study, we describe the life cycle of a free-living, wild-type, bacterivorous nematode, Caenorhabditis brenneri Sudhaus and Kiontke 2007, associated with the terrestrial slug Philippinella moellendorffi Collinge 1899 and account for the effects of food density and temperature on its population dynamics by employing the hanging drop technique. The bacterial food supply was sourced from the slug cadaver and identified as Alcaligenes faecalis (MT012081). C. brenneri was fed with varying bacterial densities (109 and 5×109 cells mL-1) and incubated at 20 and 25°C. The bacterial food density-temperature interaction was found to have no significant influence on the offspring production of C. brenneri. Moreover, the total fertility rate (TFR) and net reproductive rate (Ro) are higher in 109 cells mL-1 in both temperatures (TFR at 20°C: 139; 25°C: 169 and Ro at 20°C: 134; 25°C: 156). Whereas the alternative generation time (To, T1, T) and population doubling time (PDT) are faster at 25°C in both bacterial densities, the intrinsic rate of natural increase (rm) is faster at lower temperatures (20°C) in both bacterial densities. The average lifespan of C. brenneri is seven days when fed with A. faecalis. Offspring somatic growth (body length and width) was influenced by bacterial food density-temperature interaction with increased length and girth observed in higher bacterial density and temperature in our knowledge. This study is the first attempt to use A. faecalis, a wild-type bacterium from the terrestrial slug P. moellendorffi cadaver, as the bacterial food source for a Caenorhabditis LHT analysis.

Effects of food supply on northern bay scallops Argopecten irradians reared under two pCO2 conditions

For calcifying organisms such as bivalves, short-term exposure to increased ocean acidification (OA; elevated pCO2) may reduce growth rate, increase mortality, and disrupt shell formation. A growing body of research suggests that clearance rates and what particles bivalves select may change under high pCO2 exposure; however, these experiments are acute, ranging from days to weeks. The effects of food supply on bivalves under long-term OA exposure remain incompletely understood. In this study, juvenile northern bay scallops Argopecten irradians (Lamarck) that had been reared since 4 h post-fertilization under one of 2 OA conditions (∼500-600 or ∼750-850 µatm pCO2; ∼1.37-1.5 or ∼1.0-1.2 Ωaragonite), were subjected to 2 food levels for 42 d (low food: ∼400, high food: ∼1400 chlorophyll cells ml-1). Standard metabolic rate (SMR) and clearance rate (CR) were measured on Day 0, and SMR, CR, growth, and survivorship were measured at 14 and 42 days of exposure to 2 food levels for each of the OA treatments. Juveniles under food scarcity had reduced survivorship and growth independent of OA treatment. We found no effect of OA treatment or an OA × food interaction for these metrics. There was only a food-level effect for SMR and no OA treatment effect; however, there was an interaction between food and OA for CR. Under elevated pCO2 concentrations, scallops cleared Chaetoceros neogracile (strain Chaet-B) over Tetraselmis chui (strain PLY429) and natural seston. Altogether, these data suggest that tolerance to OA mediated by food may depend on food quality or other characteristics that influence particle selection under short-term experimental challenges.

Bacterial microbiome dynamics in commercial integrated aquaculture systems growing Ulva in abalone effluent water

In South Africa, the green seaweed Ulva lacinulata is grown in land-based integrated multi-trophic aquaculture (IMTA) farms with the abalone Haliotis midae. The Ulva serves as a biofilter and the co-produced Ulva is often used as feed for the abalone. To better understand the potential benefits and risks associated with this practice, this study characterised the bacterial microbiome associated with the seawater and Ulva raceways receiving abalone effluent (IMTA system) and compared this to Ulva tanks supplied with fertilised seawater (non-IMTA; control). Ulva samples were collected from each Ulva system, and water samples were collected at the inlet and outlet of each system. Bacterial communities were assessed using a culture-based approach and next-generation sequencing (NGS) of the V3-V4 16S rDNA region. It was observed that Ulva has the potential to reduce the bacterial load of abalone effluent, with the total number of potential culturable Vibrio species declining from 150×103 cells mL-1 in the inlet to 37×103 cells mL-1 in the outlet of the Ulva system. The NGS dataset supported these findings, with a reduction observed in Vibrio and Pseudoalteromonas from the inlet to outlet samples. A lower number of genera (p < 0.05) were observed on Ulva when compared with water samples, indicating that Ulva has a beneficial, modulatory effect on bacteria. These findings contribute towards the growing body of evidence for the benefits of seaweeds in IMTA and addresses the biosecurity concerns of abalone farmers wishing to improve the circularity of their farming activities by incorporating seaweeds.

Engineered Leukocyte Biomimetic Colorimetric Sensor Enables High-Efficient Detection of Tumor Cells Based on Bioorthogonal Chemistry.

Accurate detection of heterogeneous circulating tumor cells (CTCs) is critical as they can make tumor cells more aggressive, drug-resistant, and metastasizing. Although the leukocyte membrane coating strategy is promising in meeting the challenge of detecting heterogeneous CTCs due to its inherent antiadhesive properties, it is still limited by the reduction or loss of expression of known markers. Bioorthogonal glycol-metabolic engineering is expected to break down this barrier by feeding the cells with sugar derivatives with a unique functional group to establish artificial targets on the surface of tumor cells. Herein, an engineered leukocyte biomimetic colorimetric sensor was accordingly fabricated for high-efficient detection of heterogeneous CTCs. Compared with conventional leukocyte membrane coating, the sensor could covalently bound to the heterogeneous CTCs models fed with Ac4ManNAz in vitro through the synergy of bioorthogonal chemistry and metabolic glycoengineering, ignoring the phenotypic changes of heterogeneous CTCs. Meanwhile, a sandwich structure composed of leukocyte biomimetic layer/CTCs/MoS2 nanosheet was formed for visual detection of HeLa cells as low as 10 cells mL-1. Overall, this approach can overcome the dependence of conventional cell membrane biomimetic technology on specific cell phenotypes and provide a new viewpoint to highly efficiently detect heterogeneous CTCs.

Effects on fatty acids, biochemical composition and growth of rotifer (Brachionus plicatilis) fed with different concentrations of Nannochloropsis sp.

The density of microalgae and nutrient content have impact on the population growth rate, egg rate and nutritional values of rotifers. The aim of this study was to investigate the effects of different concentrations of the alga Nannochloropsis sp. (N10: 10x106, N20: 20x106, N30: 30x106 cells mL-1) on the growth, egg rate, biochemical composition and fatty acid profile of the rotifer Brachionus plicatilis. To maintain a consistent algae density, an equivalent quantity was supplemented to compensate for any reduction. The study was started with three replicates, each with an initial inoculation density of 200 Brachionus individuals mL-1 . The investigation spanned 5 days, during which population parameters (total number of individuals, proportion of individuals with eggs and growth rate) were calculated. After the study period, rotifers were harvested for subsequent biochemical and fatty acid analyses. Notably, the N30 group showed the highest proportions of crude protein (54.41%) and crude lipid (34.5%). The N20 group displayed the most substantial content of total fatty acids, recording a value of 70.69%. Consequently, the N30 group, with a concentration of 30x106 cells mL-1, emerged as the most proficient group, demonstrating superior performance in both population growth and biochemical composition.

PH-Responsive Biocompatible Fluorescent Hydrogel for Selective Sensing and Adsorptive Recovery of Dysprosium.

The elevated accumulation of electronic wastes, especially containing Dysprosium ion [i.e., Dy(III)], is emerging as a potential environmental threat. To overcome the deleterious effects of Dy(III), detection and removal of Dy(III) is crucial. Moreover, recovery of high-value Dy(III) is economically beneficial. However, the availability of a single material, capable of sensing Dy(III) in nanomolar concentration and simultaneously adsorbing it with high adsorption capacity (AC), is rare. Therefore, to solve this problem, a pH-responsive fluorescent amino graphene oxide-impregnated-engineered polymer hydrogel (AGO-EPH) has been synthesized, suitable for selective sensing of Dy(III) in nanomolar concentration and adsorbing it from wastewater at ambient temperature. This terpolymeric hydrogel is synthesized from two nonfluorescent monomers, propenoic acid (PNA) and prop-2-enamide (PEAM), along with an in situ generated comonomer (3-acrylamidopropanoic acid/AAPPA) through N-H activation during polymerization. Surface properties and structural details of AGO-EPH are established using NMR, FTIR, XRD, TEM, SEM, EDX, Raman, MALDI-mass, and DLS studies. The AGO-EPH exhibits blue fluorescence with selective turn-off sensing of Dy(III) with the detection limit of 1.88 × 10-7 (M). The maximum AC of AGO-EPH is 41.97 ± 0.39 mg g-1. The developed AGO-EPH shows consistent adsorption-desorption property over five cycles, with more than 90% desorption efficiency per cycle, confirming significant recovery of the valuable Dy(III). From Logic gate calculations, complexation of Dy(III) and AGO-EPH may be the reason behind fluorescence quenching. The AGO-EPH also shows antibacterial action against ∼3 × 108 cells mL-1 of E. coli solution. Overall, the developed pH-responsive engineered hydrogel can be used as a potential low-cost sensing device and reusable adsorbent for Dy(III).

Growth, Lipid, and Pigment Properties of Locally Isolated (Kastamonu, Türkiye) Chlorella sp.

Chlorella has become one of the most studied and produced microalgae, with Spirulina among the hundreds of species since the beginning of microalgal biotechnology. The growth performance of microalgae and the biochemical composition of the biomass may also vary significantly by strain. Therefore, it is thought that searching for new strains from aquatic environments is important in providing the most suitable microalgae for production. An isolated strain from Daday Stream was cultured in the laboratory at Kastamonu University. BG-11 was used as a medium, and CO2 from the air was used as a carbon source in the experiments. The initial cell number was arranged to 1.0×106 cells mL-1, and the highest cell number was found on the 17th day as 40.52×106 cells mL-1. Chlorophyll a and carotenoids were determined at the end of the experiment and were found as 3.48±0.08 µg mL-1 and 1.16±0.02 µg mL-1, respectively. Total lipid amount and fatty acid composition analysis were also conducted at the end of the study. According to the analyses, the lipid content of Chlorella sp. was found to be 15.37±0.00% (w/w). ∑SFA (saturated fatty acid), ∑MUFA (monounsaturated fatty acid), and ∑PUFA (polyunsaturated fatty acid) ratios were calculated to be 31.30±1.21%, 4.99±0.34% and 63.71±2.65%, respectively.

Viral Dynamics in the Tropical Pacific Ocean: A Comparison between Within and Outside a Warm Eddy.

In mesoscale eddies, the chemical properties and biological composition are different from those in the surrounding water due to their unique physical processes. The mechanism of physical-biological coupling in warm-core eddies is unclear, especially because no studies have examined the effects of environmental factors on bacteria and viruses. The purpose of the present study was to examine the influence of an anticyclonic warm eddy on the relationship between bacterial and viral abundances, as well as viral activity (viral production), at different depths. At the core of the warm eddy, the bacterial abundance (0.48 to 2.82 × 105 cells mL-1) fluctuated less than that outside the eddy (1.12 to 7.03 × 105 cells mL-1). In particular, there was a four-fold higher viral-bacterial abundance ratio (VBR) estimated within the eddy, below the layer of the deep chlorophyll maximum, than outside the eddy. An anticyclonic warm eddy with downwelling at its center may contribute to viruses being transmitted directly into the deep ocean through adsorption on particulate organic matter while sinking. Overall, our findings provide valuable insights into the interaction between bacterial and viral abundances and their ecological mechanisms within a warm eddy.

Bacterial community and cyanotoxin gene distribution of the Winam Gulf, Lake Victoria, Kenya.

The Winam Gulf (Kenya) is frequently impaired by cyanobacterial harmful algal blooms (cHABs) due to inadequate wastewater treatment and excess agricultural nutrient input. While phytoplankton in Lake Victoria have been characterized using morphological criteria, our aim is to identify potential toxin-producing cyanobacteria using molecular approaches. The Gulf was sampled over two successive summer seasons, and 16S and 18S ribosomal RNA gene sequencing was performed. Additionally, key genes involved in production of cyanotoxins were examined by quantitative PCR. Bacterial communities were spatially variable, forming distinct clusters in line with regions of the Gulf. Taxa associated with diazotrophy were dominant near Homa Bay. On the eastern side, samples exhibited elevated cyrA abundances, indicating genetic capability of cylindrospermopsin synthesis. Indeed, near the Nyando River mouth in 2022, cyrA exceeded 10 million copies L-1 where there were more than 6000 Cylindrospermopsis spp. cells mL-1. In contrast, the southwestern region had elevated mcyE gene (microcystin synthesis) detections near Homa Bay where Microcystis and Dolichospermum spp. were observed. These findings show that within a relatively small embayment, composition and toxin synthesis potential of cHABs can vary dramatically. This underscores the need for multifaceted management approaches and frequent cyanotoxin monitoring to reduce human health impacts.

Quantifying the Potential for Nitrate-Dependent Iron Oxidation on Early Mars: Implications for the Interpretation of Gale Crater Organics.

Geological evidence and atmospheric and climate models suggest habitable conditions occurred on early Mars, including in a lake in Gale crater. Instruments aboard the Curiosity rover measured organic compounds of unknown provenance in sedimentary mudstones at Gale crater. Additionally, Curiosity measured nitrates in Gale crater sediments, which suggests that nitrate-dependent Fe2+ oxidation (NDFO) may have been a viable metabolism for putative martian life. Here, we perform the first quantitative assessment of an NDFO community that could have existed in an ancient Gale crater lake and quantify the long-term preservation of biological necromass in lakebed mudstones. We find that an NDFO community would have the capacity to produce cell concentrations of up to 106 cells mL-1, which is comparable to microbes in Earth's oceans. However, only a concentration of <104 cells mL-1, due to organisms that inefficiently consume less than 10% of precipitating nitrate, would be consistent with the abundance of organics found at Gale. We also find that meteoritic sources of organics would likely be insufficient as a sole source for the Gale crater organics, which would require a separate source, such as abiotic hydrothermal or atmospheric production or possibly biological production from a slowly turning over chemotrophic community.