The Antimicrobial Activity of Combination of Vitamin D3 and Omega-3 against Pathogenic Microorganisms.

BACKGROUND: Food supplements such as vitamin D3 and omega-3 have a significant role in activating the immune system and impacting the diversity of gut microbiota; thus, controlling the growth of invading pathogens indirectly. OBJECTIVE: This study aims to evaluate the direct antimicrobial activity of vitamin D3 and omega- 3 individually, combined together, and combined with low concentrations of gentamicin or amphotericin B against selected pathogenic microorganisms. In addition, this study hypothesizes the potential antimicrobial mechanism and recommends suitable studies to be conducted. METHOD: Minimum inhibitory concentration of different serial dilutions of vitamin D3 [0.7µg/mL-83.3µg/mL] or omega-3 [0.7mg/mL-100mg/mL] or combined [vitamin D3:1.3µg/mL-83.3µg/mL and omega-3:1.56mg/mL-100mg/mL] with/without antibiotic have been investigated on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans using check board technique. RESULTS: The highest concentration of vitamin D3 [83.3 µg/mL] demonstrated a complete eradication of the tested microorganisms. Conversely, omega-3 had a lower effect on them. The highest concentration of combining vitamin D3 and omega-3 with/without gentamicin resulted in a complete eradication of the S. aureus, E. coli and P. aeruginosa with a 6.8 to 7 log reduction. On the other hand, C. albicans was inhibited when using vitamin D3 [83.3 µg/mL] or when this concentration is combined with 100mg/mL of omega-3. However, when these two concentrations were added to amphotericin B the log reduction dropped to 0.45 suggesting antagonistic effect. CONCLUSION: These findings suggested that, unlike omega 3, vitamin D3 possesses good antimicrobial effects against pathogenic microorganisms. The combination of the studied food supplement showed enhanced microbial inhibition at high concentration, while they had antagonistic effect when combined with amphotericin B and applied on C. albicans combined. Further studies on the exact antimicrobial mechanism are still required to understand the measured data here.

Evaluation of immunomodulatory potential of probiotic conditioned medium on murine macrophages.

Probiotics are a mixture of beneficial live bacteria and/or yeasts that naturally exist in our bodies. Recently, numerous studies have focused on the immunostimulatory effects of single-species or killed multi-species probiotic conditioned mediums on macrophages. This study investigates the immunostimulatory effect of commercially available active, multi-species probiotic conditioned medium (CM) on RAW264.7 murine macrophages. The probiotic CM was prepared by culturing the commercially available probiotic in a cell-culture medium overnight at 37 °C, followed by centrifugation and filter-sterilization to be tested on macrophages. The immunostimulatory effect of different dilution percentages (50%, 75%, 100%) of CM was examined using the MTT assay, proinflammatory cytokine (tumor necrosis factor TNF-alpha) production in macrophages, migration, and phagocytosis assays. For all the examined CM ratios, the percentages of cell viability were > 80%. Regarding the migration scratch, TNF-alpha and phagocytosis assays, CM demonstrated a concentration-dependent immunostimulatory effect. However, the undiluted CM (100%) showed a significant (p-value < 0.05) stimulatory effect compared to the positive and negative controls. The findings suggest that the secretions and products of probiotics, as measured in the CM, may be closely associated with their immune-boosting effects. Understanding this relationship between probiotic secretions and immune function is crucial for further exploring the potential benefits of probiotics in enhancing overall health and well-being.

Potential of Natural Phenolic Compounds as Antimicrobial Agents against Multidrug-Resistant Staphylococcus aureus in Chicken Meat.

Staphylococcus aureus is one of the most widespread foodborne bacteria that cause high morbidity, mortality, and economic loss, primarily if foodborne diseases are caused by pathogenic and multidrug-resistant (MDR) strains. This study aimed to determine the prevalence of S. aureus in chicken meat in Egyptian markets. Thus, this study might be the first to assess the efficiency of different natural phenolic compounds as novel antibacterial agents against MDR S. aureus pathogens isolated from raw chicken meat in the Egyptian market. The incidence and quantification of pathogenic S. aureus were detected in retail raw chicken meat parts (breast, thigh, fillet, and giblets). In total, 73 out of 80 (91.3%) of the chicken meat parts were contaminated, with S. aureus as the only species isolated. Of the 192 identified S. aureus isolates, 143 were coagulase-positive S. aureus and 117 isolates were MDR (81.8%, 117/143). Twenty-two antibiotic resistance profile patterns were detected. One strain was randomly selected from each pattern to further analyze virulence and resistance genes. Extracted DNA was assessed for the presence of antibiotic-resistance genes, i.e., vancomycin-resistance (vanA), aminoglycosides-resistance (aacA-aphD), apramycin-resistance (apmA), and methicillin-resistance (mecA), penicillin-resistance (blaZ), and virulence genes staphylococcal enterotoxins (sea and seb), Panton-Valentine leucocidin (pvl), clumping factor A (clfA), and toxic shock syndrome toxin (tst). Clustering analyses revealed that six S. aureus strains harbored the most virulence and resistance genes. The activity of hydroquinone was significantly higher than thymol, carvacrol, eugenol, and protocatechuic acid. Therefore, phenolic compounds, particularly hydroquinone, could potentially alternate with conventional antibiotics against the pathogenic MDR S. aureus inhabiting raw chicken meat. Hence, this study indicates that urgent interventions are necessary to improve hygiene for safer meat in Egyptian markets. Moreover, hydroquinone could be a natural phenolic compound for inhibiting foodborne pathogens.

In vivo tests of a novel wound dressing based on agar aerogel.

Aerogels, especially bio-based ones, present a promising option for wound dressing; specifically, because of their low toxicity, high stability, bio-compatibility, and good biological performance. In this study, agar aerogel was prepared and evaluated as novel wound dressing material in an in vivo rat study. Agar hydrogel was prepared by thermal gelation, after that the water inside the gel was exchanged with ethanol, and finally the alcogel was dried by supercritical CO2. The textural and rheological properties of the prepared aerogel were characterized, showing that the prepared agar aerogels possess high porosity (97-98 %), high surface area (250-330 m2g-1) as well as good mechanical properties and easiness of removal from the wound site. The results of the in vivo experiments macroscopically demonstrate the tissue compatibility of the aerogels in dorsal interscapular injured rat tissue and a shorter wound healing time comparable to that of gauze-treated animals. The histological analysis underpins the reorganisation and healing of the tissue for the injured skin of rats treated with agar aerogel wound dressing within the studied time frame.

A comprehensive clinical guide for Pneumocystis jirovecii pneumonia: a missing therapeutic target in HIV-uninfected patients.

INTRODUCTION: Pneumocystis jirovecii is an opportunistic, human-specific fungus that causes Pneumocystis pneumonia (PCP). PCP symptoms are nonspecific. A patient with P. jirovecii and another lung infection faces a diagnostic challenge. It may be difficult to determine which of these agents is responsible for the clinical symptoms, preventing effective treatment. Diagnostic and treatment efforts have been made more difficult by the rising frequency with which coronavirus 2019 (COVID-19) and PCP co-occur. AREAS COVERED: Herein, we provide a comprehensive review of clinical and pharmacological recommendations along with a literature review of PCP in immunocompromised patients focusing on HIV-uninfected patients. EXPERT OPINION: PCP may be masked by identifying co-existing pathogens that are not necessarily responsible for the observed infection. Patients with severe form COVID-19 should be examined for underlying immunodeficiency, and co-infections must be considered as co-infection with P. jirovecii may worsen COVID-19's severity and fatality. PCP should be investigated in patients with PCP risk factors who come with pneumonia and suggestive radiographic symptoms but have not previously received PCP prophylaxis. PCP prophylaxis should be explored in individuals with various conditions that impair the immune system, depending on their PCP risk.

Evaluation of hepatitis B knowledge, practices, and beliefs among the Jordanian population: A cross-sectional study.

This study aimed to assess the knowledge, practices, and beliefs among the Jordanian population regarding hepatitis B virus (HBV) infection. A cross-sectional questionnaire was designed and used to recruit participants from October 5th through December 12th. Statistical analysis was conducted using SPSS. Descriptive statistical analysis was used to analyse the sociodemographic data, the Shapiro-Wilk test was used to assess the normality, Cronbach's α was used to evaluate the reliability of the questionnaire and Point-biserial correlation was used to figure out whether there is an association between Score of knowledge and the dichotomous variables. A random sample of 432 participated in the study. The majority were females (n = 310, 71.8%), the mean age was 21 (42.0%) years,416 (96.3%) were urban inhabitants and most of them (n = 351, 81.3%) had bachelor's degree. School/university (n = 280, 64.8%) were reported as a major source of information followed by TV/internet/social media 276 (63.9%). The total mean (± SD) of knowledge score regarding HBV infection symptoms, transmission modes and treatment was found 12.28 ± 3.2. Participants' knowledge regarding symptoms including nausea, vomiting and loss of appetite was 73 (16.9%). More than 80% had good knowledge regarding the complications of HBV infection. Only 100 participant reported vaccination (23.1%) against the virus. Poor knowledge and low vaccination rate against HBV were found thus implementing comprehensive educational program for people highlighting the importance of vaccination against the virus is crucial.

Time-Series Analysis and Healthcare Implications of COVID-19 Pandemic in Saudi Arabia.

The first case of coronavirus disease 2019 (COVID-19) in Saudi Arabia was reported on 2 March 2020. Since then, it has progressed rapidly and the number of cases has grown exponentially, reaching 788,294 cases on 22 June 2022. Accurately analyzing and predicting the spread of new COVID-19 cases is critical to develop a framework for universal pandemic preparedness as well as mitigating the disease's spread. To this end, the main aim of this paper is first to analyze the historical data of the disease gathered from 2 March 2020 to 20 June 2022 and second to use the collected data for forecasting the trajectory of COVID-19 in order to construct robust and accurate models. To the best of our knowledge, this study is the first that analyzes the outbreak of COVID-19 in Saudi Arabia for a long period (more than two years). To achieve this study aim, two techniques from the data analytics field, namely the auto-regressive integrated moving average (ARIMA) statistical technique and Prophet Facebook machine learning technique were investigated for predicting daily new infections, recoveries and deaths. Based on forecasting performance metrics, both models were found to be accurate and robust in forecasting the time series of COVID-19 in Saudi Arabia for the considered period (the coefficient of determination for example was in all cases more than 0.96) with a small superiority of the ARIMA model in terms of the forecasting ability and of Prophet in terms of simplicity and a few hyper-parameters. The findings of this study have yielded a realistic picture of the disease direction and provide useful insights for decision makers so as to be prepared for the future evolution of the pandemic. In addition, the results of this study have shown positive healthcare implications of the Saudi experience in fighting the disease and the relative efficiency of the taken measures.

Variations in the respiratory microbiota amongst asthmatic and non-asthmatic subjects in Jordan.

In this work, variation in microbiota in the lower respiratory tract (LRT) among asthmatic and non-asthmatic subjects is identified. All participants (27 asthmatic patients and 27 non-asthmatic subjects) were asked to expectorate a sputum sample in special sterile tubes after rinsing the mouth with a sterilizing solution. The expectorated sputum specimen was immediately homogenized and stored in the deep freezer for DNA extraction for microbial gene sequencing and sequence analyses. For sequencing the V4 region of the 16S rRNA gene was sequenced using Illumina MiSeq, followed by an analysis of alpha and beta diversity. It was found that asthmatic patients had greater bacterial diversity than non-asthmatic subjects. Bacteria associated to the phyla (Bacteroidetes, Proteobacteria, and Firmicutes) accounted for 90 % of all sequences. The relative abundance of Proteobacteria in the asthmatic patients was higher than that of non-asthmatic (30 % vs 17 %; P-value = 0.044), along with a high abundance of the pathogen Haemophilus influenza. In contrast, Firmicutes (41 %) and Bacteroidetes (31 %) showed higher relative abundances in the non-asthmatic subjects. No significant link was found between the type of asthma drug or the method of drug usage (orally or via inhalation) and the respiratory microbiota. Therefore, the variations in LRS microbiota are not caused by the drugs taken by the asthmatic patients, rather they might be connected to the etiology of asthma. Since the asthmatic patients had higher proportions of Haemophilus influenzae, these organisms could be a causative factor in the pathophysiology of asthma.

Menstrual changes following COVID-19 infection: A cross-sectional study from Jordan and Iraq.

PURPOSE: COVID-19 infection is normally followed by several post-COVID effects. This study aimed to investigate to evaluate menstrual changes in females following COVID-19 infection, and to evaluate female perception about the effect of COVID-19 on their menstrual cycles. METHODS: During this cross-sectional survey-based study, a convenience sample of 483 women from Jordan and from Iraq, who had infected with COVID-19 were invited to fill-out the study questionnaire. RESULTS: The study was conducted on the females, with a median age 31 years old. Results showed that 47.2% of them (n = 228) suffered from a change in the number of days between two consecutive periods, as well as from a change in the amount of blood loss. Also, more than 50% of them believed that COVID-19 infection may cause changes in the amount of blood loss during the cycle (n = 375, 56.9%), and changes in the number of days between the two consecutive periods (n = 362, 54.2%). Regression analysis showed that participants with higher educational level (bachelor or higher) (Beta = -0.114, P = 0.011), and those living in Iraq (Beta = -0.166, P<0.001) believed that COVID-19 has lower tendency to cause menstrual changes. In addition, non-married females (Beta = 0.109, P = 0.017), and those who are current smokers (Beta = 0.091, P = 0.048) believed that COVID-19 has higher tendency to cause menstrual changes. CONCLUSION: his study revealed that COVID-19 infection could affect the menstrual cycle for the females. Further prospective studies should be done to confirm these findings and evaluate how long these menstrual irregularities lasted.

Patterns of antibiotic use, knowledge, and perceptions among different population categories: A comprehensive study based in Arabic countries.

Background: Antibiotics are essential for the treatment of bacterial infections and are considered among the most commonly sold drug classes from the community pharmacy in the developing countries without a prescription in most cases. Purpose: This study aims to explore the knowledge, practices, and attitudes regarding antibiotic use. Materials and methods: This study employs a cross-sectional descriptive design that used a pre-validated survey. The participants were classified into three main mutually exclusive groups: healthcare professionals, medical students, and other adults in the community. Results: Of the 10,226 participants, 1157 (11%) were healthcare professionals; 2322 (23%) were medical students and 6747 (66%) were other adults in community. The majority of participants used antibiotic at least once during the past year. A total of 838 (72.4%) healthcare professionals and 800 (34.5%) medical students had prescribed an antibiotic during the last 6 months.Almost half of the medical students and adults in the community and almost one-third of healthcare professionals reported that the aim of antibiotics use is for fever. Furthermore, around one-quarter of participants reported that the aim of antibiotics use is for viral infection. Around one-quarter of respondents stated that the antibiotic will always be effective in the treatment of the same infection in the future. Around one-quarter of participants stated that 21 to 50% of antibiotics are considered to be unnecessary or inappropriate prescriptions. Different factors were perceived as being very important causes of antibiotic resistance among the participants. Conclusions: These findings indicated that this study participants showed unsatisfactory knowledge and perceptions of proper antibiotic use. Therefore, there is a requirement for a comprehensive and effective antibiotic-stewardship program to promote rational antibiotics use, and compensate for knowledge and perceptions gaps to prevent antibiotic resistance development.

Investigation on Antimicrobial, Antioxidant, and Anti-cancerous activity of Agaricus bisporus derived ß-Glucan particles against cervical cancer cell line.

Cervical cancer is one of the leading causes of death among women. Due to incomplete knowledge and hidden symptoms, it is not easily diagnosable. After the diagnosis of cervical cancer at an advanced stage, treatment such as chemotherapy and radiation therapy become too much costly along with having many side effects such as hair loss, loss of appetite, nausea, tiredness, etc. ß-Glucan does a novel polysaccharide has many immunomodulatory properties. In our research, we have tested the efficacy of Agaricus bisporus derived ß-Glucan particles (ADGPs) as an antimicrobial, antioxidant and anticancer agent against the cervical cancer HeLa cells. Prepared particles were quantified for carbohydrate content by anthrone test and further HPTLC analysis to confirm the polysaccharide nature and 1,3 glycosidic linkages of ß-Glucan. ADGPs were found to have efficient antimicrobial activity against various fungal and bacterial tested strains. DPPH assay confirmed the antioxidant activity of ADGPs. Cell viability was assessed against the cervical cancer cell line by using the MTT and IC50 was found at 54µg/ml. Furthermore, ß-Glucan was found to induce a significant amount of ROS, leading to the apoptosis of cells. The same was also assessed with the help of Propidium Iodide (PI) staining. With the help of JC-1 staining, ß-Glucan was found to disrupt the Mitochondrial Membrane Potential (MMP), ultimately resulting in the cancer cell HeLa death. Based on our experimental findings, we found that ADGPs can be proven as an efficient therapy for cervical cancer treatment and work as an antimicrobial and antioxidant agent.

Role of Natural plant extracts for potential Antileishmanial targets-In-depth review of the molecular mechanism.

A group of protozoan parasites known as Leishmania species can cause a variety of chronic illnesses, ranging from self-healing lesions to fatal outcomes. Drug-resistant pathogens have become common due to the lack of safe and effective medications, which has sparked the development of new therapeutic interventions, particularly plant-based natural extracts. As a way to avoid chemotherapy's side effects, natural herbal remedies have drawn more attention. In addition to having anti-inflammatory, anticancer, and cosmetic properties, the secondary metabolites of plants, such as phenolic compounds, flavonoids, alkaloids, and terpenes, have a number of positive effects on our health. Natural metabolites such as naphthoquinone, alkaloids, benzophenones, etc. that have antileishmanial and antiprotozoal activity have been the subject of extensive research. In this review paper, it can be concluded that these natural extracts can be developed into excellent therapeutic agents against Leishmaniasis.

Unveiling Antioxidant and Antiproliferative Effects of Prosopis juliflora Leaves against Human Prostate Cancer LNCaP Cells.

Herbal medications or formulations are regularly recommended by clinicians as a potential therapeutic method for a variety of human ailments, including cancer. Although Prosopis juliflora extracts have shown promise in anticancer activity, the effects on prostate cancer and the accompanying molecular mechanisms of action are still unexplored. This research aims at the antioxidant, antiproliferative, and apoptosis-inducing properties of Prosopis juliflora methanolic leaves extract in human prostate cancer LNCaP cells. The antioxidant ability of the extract was assessed using the DPPH (2, 2-diphenyl-2-picrylhydrazyl) and two additional reducing power tests. Antitumor activity was determined using MTT cell viability tests and LDH cytotoxicity assays. The probable mechanism of apoptotic cell death was further investigated utilizing a caspase-3 activation assay and qRT-PCR mRNA expression investigations of apoptotic-related genes. The results revealed that the methanol extract of Prosopis juliflora leaves contains alkaloids, flavonoids, tannins, glycosides, and phenols, all of which have substantial antioxidant activity. In vitro anticancer tests demonstrated that extract therapy resulted in a dose-dependent reduction in cell viability of LNCaP prostate cancer cells, but normal HaCaT cells showed no cytotoxic effects. Furthermore, plant extract therapy increased caspase-3 activation and mRNA expression of apoptotic-related genes, suggesting that this could be a mechanism for cancer cell growth suppression. The significance of Prosopis juliflora as a source of new antioxidant compounds against prostate cancer was emphasized in the current study. However, more study is needed to demonstrate the efficacy of Prosopis juliflora leaves extract in the treatment of prostate cancer.

Evaluation of the orally administered calcium alginate aerogel on the changes of gut microbiota and hepatic and renal function of Wistar rats.

The present study evaluates the effect of calcium alginate aerogel as a potential drug carrier, on the liver and kidney functions, and on the gut microbiota of Wistar rats. The studied alginate aerogel was prepared in the form of nanoparticles using the jet cutting technique, and they were characterized in terms of specific surface areas, outer morphology and particle size distribution. For the in vivo study, calcium alginate aerogel was administered orally, and liver and kidney functions were tested for one week and for four weeks in two distinct studies. During the short-term in vivo study, feces samples were collected for bacterial DNA extraction followed by 16S rRNA gene sequencing analyses to detect changes in gut microbiota. Results showed that the prepared alginate aerogel has an average BET-specific surface area of around 540 m2/g, with a pore volume of 7.4 cc/g, and pore width of 30-50 nm. The in vivo study revealed that the levels of the studied kidney and liver enzymes didn't exceed the highest level of the normal range. The study of gut microbiota showed different patterns; certain groups of bacteria, such as Clostridia and Bacteriodia, increased during the aerogels regime and continued to increase after the aerogel was stopped. While other groups such as Erysipelotrichia, and Candidatus saccharibacteria increased during aerogels treatment, and then decreased again after one month. Members of the Bacilli class showed a unique trend, that is, after being the most abundant group (63%) at time 0, their relative abundance decreased dramatically until it reached < 5%; which was the case even after stopping the aerogel treatment.

Prevalence, knowledge of and attitude towards hepatitis B virus among pregnant females in Jordan.

This observational study was designed to assess the prevalence, knowledge and attitude of pregnant females towards hepatitis B infection, in addition to their perspective of the healthcare practice about HBV in Jordan. A randomly selected group of pregnant females visiting public gynaecology clinics in Jordan were approached to participate in the study. Blood samples were collected from the participants, and HBV markers were detected in their serum using specialized ELISA Kits to assess for the prevalence of infection. Knowledge and attitude of participants was assessed via a developed and validated questionnaire. Statistical analysis was conducted using the Statistical Package for the Social Sciences (SPSS) version 24. Blood samples (n = 300) from 330 pregnant females were collected. The prevalence of hepatitis B surface antigen (HBsAg) among the pregnant females was found to be 5%. Anti-HBs and anti-HBc were found to be 33.3% and 7%, respectively. No significant correlation between age, socio-economic status and educational level was found with HBsAg positivity. Limited knowledge regarding HBV was revealed among the pregnant females (9.1%-41.3%, P < .05). The majority had a positive attitude regarding HBV vaccination and antiviral medications in case of infectivity. More than 90% agreed on the present lack of counselling and screening of HBV they obtained during their first perinatal visit to the gynaecology clinics. This study revealed a lack of knowledge on HBV, and low counselling and screening received were reported. Policymakers need to introduce new interventions to improve the current awareness of patients and gynaecologists regarding hepatitis B infection.

Anoxygenic photosynthesis controls oxygenic photosynthesis in a cyanobacterium from a sulfidic spring.

Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 (-) during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life.

Rapid Reactivation of Cyanobacterial Photosynthesis and Migration upon Rehydration of Desiccated Marine Microbial Mats.

Desiccated cyanobacterial mats are the dominant biological feature in the Earth's arid zones. While the response of desiccated cyanobacteria to rehydration is well-documented for terrestrial systems, information about the response in marine systems is lacking. We used high temporal resolution hyperspectral imaging, liquid chromatography, pulse-amplitude fluorometry, oxygen microsensors, and confocal laser microscopy to study this response in a desiccated microbial mat from Exmouth Gulf, Australia. During the initial 15 min after rehydration chlorophyll a concentrations increased 2-5 fold and cyanobacterial photosynthesis was re-established. Although the mechanism behind this rapid increase of chlorophyll a remains unknown, we hypothesize that it involves resynthesis from a precursor stored in desiccated cyanobacteria. The subsequent phase (15 min-48 h) involved migration of the reactivated cyanobacteria toward the mat surface, which led, together with a gradual increase in chlorophyll a, to a further increase in photosynthesis. We conclude that the response involving an increase in chlorophyll a and recovery of photosynthetic activity within minutes after rehydration is common for cyanobacteria from desiccated mats of both terrestrial and marine origin. However, the response of upward migration and its triggering factor appear to be mat-specific and likely linked to other factors.

Spatial patterns and links between microbial community composition and function in cyanobacterial mats.

We imaged reflectance and variable fluorescence in 25 cyanobacterial mats from four distant sites around the globe to assess, at different scales of resolution, spatial variabilities in the physiological parameters characterizing their photosynthetic capacity, including the absorptivity by chlorophyll a (A chl), maximum quantum yield of photosynthesis (Y max), and light acclimation irradiance (I k). Generally, these parameters significantly varied within individual mats on a sub-millimeter scale, with about 2-fold higher variability in the vertical than in the horizontal direction. The average vertical profiles of Ymax and I k decreased with depth in the mat, while A chl exhibited a sub-surface maximum. The within-mat variability was comparable to, but often larger than, the between-sites variability, whereas the within-site variabilities (i.e., between samples from the same site) were generally lowest. When compared based on averaged values of their photosynthetic parameters, mats clustered according to their site of origin. Similar clustering was found when the community composition of the mats' cyanobacterial layers were compared by automated ribosomal intergenic spacer analysis (ARISA), indicating a significant link between the microbial community composition and function. Although this link is likely the result of community adaptation to the prevailing site-specific environmental conditions, our present data is insufficient to identify the main factors determining these patterns. Nevertheless, this study demonstrates that the spatial variability in the photosynthetic capacity and light acclimation of benthic phototrophic microbial communities is at least as large on a sub-millimeter scale as it is on a global scale, and suggests that this pattern of variability scaling is similar for the microbial community composition.

Community structure and activity of a highly dynamic and nutrient-limited hypersaline microbial mat in Um Alhool Sabkha, Qatar.

The Um Alhool area in Qatar is a dynamic evaporative ecosystem that receives seawater from below as it is surrounded by sand dunes. We investigated the chemical composition, the microbial activity and biodiversity of the four main layers (L1-L4) in the photosynthetic mats. Chlorophyll a (Chl a) concentration and distribution (measured by HPLC and hyperspectral imaging, respectively), the phycocyanin distribution (scanned with hyperspectral imaging), oxygenic photosynthesis (determined by microsensor), and the abundance of photosynthetic microorganisms (from 16S and 18S rRNA sequencing) decreased with depth in the euphotic layer (L1). Incident irradiance exponentially attenuated in the same zone reaching 1% at 1.7-mm depth. Proteobacteria dominated all layers of the mat (24%-42% of the identified bacteria). Anoxygenic photosynthetic bacteria (dominated by Chloroflexus) were most abundant in the third red layer of the mat (L3), evidenced by the spectral signature of Bacteriochlorophyll as well as by sequencing. The deep, black layer (L4) was dominated by sulfate reducing bacteria belonging to the Deltaproteobacteria, which were responsible for high sulfate reduction rates (measured using 35S tracer). Members of Halobacteria were the dominant Archaea in all layers of the mat (92%-97%), whereas Nematodes were the main Eukaryotes (up to 87%). Primary productivity rates of Um Alhool mat were similar to those of other hypersaline microbial mats. However, sulfate reduction rates were relatively low, indicating that oxygenic respiration contributes more to organic material degradation than sulfate reduction, because of bioturbation. Although Um Alhool hypersaline mat is a nutrient-limited ecosystem, it is interestingly dynamic and phylogenetically highly diverse. All its components work in a highly efficient and synchronized way to compensate for the lack of nutrient supply provided during regular inundation periods.

Light utilization efficiency in photosynthetic microbial mats.

Based on combined microsensor measurements of irradiance, temperature and O(2) , we compared light energy budgets in photosynthetic microbial mats, with a special focus on the efficiency of light energy conservation by photosynthesis. The euphotic zones in the three studied mats differed in their phototrophic community structure, pigment concentrations and thickness. In all mats, < 1% of the absorbed light energy was conserved via photosynthesis at high incident irradiance, while the rest was dissipated as heat. Under light-limiting conditions, the photosynthetic efficiency reached a maximum, which varied among the studied mats between 4.5% and 16.2% and was significantly lower than the theoretical maximum of 27.7%. The maximum efficiency correlated linearly with the light attenuation coefficient and photopigment concentration in the euphotic zone. Higher photosynthetic efficiency was found in mats with a thinner and more densely populated euphotic zone. Microbial mats exhibit a lower photosynthetic efficiency compared with ecosystems with a more open canopy-like organization of photosynthetic elements, where light propagation is not hindered to the same extent by photosynthetically inactive components; such components contributed about 40-80% to light absorption in the investigated microbial mats, which is in a similar range as in oceanic planktonic systems.