Acclimation responses of hydrogen producing cyanobacteria

During recent years, cyanobacteria have been gaining popularity rapidly as a platform for CO2 sequestration and production of a wide range of industrially attractive products. Factors such as simple nutritional requirements, flexibility to genetic manipulations and ability to adapt to fluctuating environmental conditions make these organisms suitable for bioindustrial processes that could be leveraged to address earthbound challenges like climate change and extraterrestrial ambitions like long‐term manned missions to space. The main objective of this thesis was to improve our understanding of the growth and cellular acclimation of cyanobacteria in response to specific environmental conditions such as N deficiency leading to the improved H2 photoproduction yield and simulated Martian atmosphere. The research activities extended from cyanobacterial cultivation for biomass accumulation, CO2 sequestration and production of some valuable metabolites, such as carbohydrates and carotenoids to conversion of solar energy into energy of hydrogen biofuel by alginate‐entrapped cultures. Major part of my research was dedicated to optimization of a biohydrogen production platform using heterocystous cyanobacteria. I evaluated possible routes to prolong H2 photoproduction in native (Calothrix 336/3) and model (Anabaena PCC 7120, ΔhupL) strains of cyanobacteria entrapped in Ca2+‐ alginate films. Periodic supplementation of nitrogen through addition of air, or air + 6% CO2 was shown to restore the photosynthetic activity of the entrapped cells and increased the H2 production yields in Calothrix 336/3 and ΔhupL cells (excluding air + 6% CO2). Despite obvious recovery of the photosynthetic activity, the H2 photoproduction yields did not alter post air‐treatments of the wild‐type Anabaena PCC 7120, which could be linked to the presence of active uptake hydrogenase recycling H2. In general, Calothrix showed a more stable photosynthetic apparatus and resilience to H2 photoproducing conditions. Such robustness is most probably determined by an efficient reactive oxygen species scavenging network. Indeed, characterization of carotenogenesis pathway in Calothrix 336/3 showed high content of hydroxycarotenoids that are efficient antioxidants. Research revealed that alginate‐entrapped cyanobacteria under H2 photoproducing conditions tend to employ strain‐specific strategies to counteract the C/N imbalance and oxidative stress, especially when exposed over extended periods. Further, my research proposed the prominent role of the uptake hydrogenase enzyme in photoprotection of the filaments during stress conditions such as the long‐term N‐deprivation. Part of my research was focused on the growth and acclimation of unicellular and heterocystous filamentous cyanobacteria under a low‐pressure atmosphere simulating Martian (< 1 atm, N‐limitation, high CO2) conditions. Here, the availability of CO2 and N2, and the presence or absence of O2 showed an effect on the growth and heterocyst formation in cyanobacteria, in an interdependent manner. The tested strains were able to tolerate 100% CO2 in atmospheric pressures as low as 100 mbars. To summarize, my results show that the acclimation responses of H2 producing cyanobacteria to various stress‐inducing conditions are indeed strain specific. In depth understanding of such behavior is especially important to consider when designing a commercially inclined platform incorporating cyanobacteria.Nykyisin hiilidioksidin sitominen ilmakehästä sekä monien erilaisten kaupallisesti kiinnostavien yhdisteiden tuotto tapahtuu yhä useammin syanobakteereiden avulla. Syanobakteerien ravinnevaatimukset ovat yksinkertaiset, niitä on mahdollista muunnella geneettisesti ja ne kykenevät sopeutumaan vaihteleviin ympäristöolosuhteisiin. Nämä ominaisuudet tekevät tästä organismista sopivan erilaisiin bioteollisuuden sovelluksiin, jotka pyrkivät vastaamaan sellaisiin haasteisiin kuten ilmastonmuutos tai pitkäkestoiset miehitetyt avaruuslennot. Väitöstutkimukseni päätavoite oli lisätä ymmärrystämme syanobakteerien kasvusta ja sopeutumisesta tiettyihin ympäristöoloihin kuten typenpuutteeseen, jolloin monien syanobakteerien vedyntuotto valossa lisääntyy, sekä Marsin ilmakehää muistuttaviin oloihin. Kokeet käsittivät syanobakteerien kasvatusta biomassan tuotantoa, hiilidioksidin sitomista ilmakehästä ja erinäisten arvokkaiden lopputuotteiden kuten hiilihydraattien ja karotenoidien tuottoa varten sekä lisäksi vedyntuottoa aurinkoenergian avulla alginaatille kiinnitetyissä syanobakteereissa. Merkittävä osa tutkimuksestani keskittyi heterokystejä muodostavien syanobakteerien vedyntuoton optimointiin. Arvioin erilaisia keinoja pidentää Ca2+‐alginaattifilmien sisällä kasvavien syanobakteerien vedyntuottoa käyttäen kotoperäistä syanobakteeria (Calothrix 336/3) sekä malliorganismia (Anabaena PCC 7120, ΔhupL). Jaksottainen typenlisäys, altistamalla kasvatus ilmalle tai ilmalle jossa on 6 % hiilidioksidia, palautti solujen fotosynteesiaktiivisuuden ja paransi vedyntuottoa Calothrix 336/3 sekä ΔhupL ‐kannoissa (lukuunottamatta käsittelyä ilma + 6 % CO2). Huolimatta fotosynteesiaktiivisuuden palautumisesta Anabaena PCC 7120 ‐villityypin vedyntuotto ei lisääntynyt, mikä johtunee vetyä kuluttavan hydrogenaasin (engl. uptake hydrogenase) aktiivisuudesta. Calothrix‐syanobakteerin yhteytyskoneisto kesti muita testattuja kantoja paremmin olosuhteita, joissa vedyntuotto lisääntyi, mikä todennäköisesti johtui tehokkaasta reaktiivisten happiyhdisteiden vaimentumisesta. Calothrix 336/3 syanobakteerin karoteenisynteesin tutkiminen paljastikin suuren määrän hydroksikarotenoideja, jotka ovat tehokkaita antioksidantteja. Tutkimukseni paljasti että olosuhteissa, jotka johtavat tehokkaaseen vedyntuotantoon, alginaatissa kasvavat syanobakteerit käyttävät organismista riippuen erilaisia strategioita selvitäkseen epäoptimaalisesta C/N‐suhteesta sekä hapettavasta stressistä, erityisesti kun olosuhteet jatkuvat pidemmän aikaa. Lisäksi tutkimusteni perusteella vetyä kuluttavalla hydrogenaasilla on tärkeä merkitys filamenttien suojautumisessa valolta stressioloissa kuten pitkäaikaisessa typenpuutteessa. Osa tutkimuksestani keskittyi yksisoluisten tai heterokystejä ja filamentteja muodostavien syanobakteerien kasvuun ja sopeutumiseen olosuhteissa, jotka jäljittelivät Marsin ilmakehää (>yhden ilmakehän paine, vähäinen typen määrä, suuri hiilidioksidipitoisuus). Hiilidioksidin ja typpikaasun saatavuus sekä hapen saatavuus vaikuttivat syanobakteerien kasvuun ja heterokystien muodostumiseen. Testatut kannat pystyivät sietämään 100 % hiilidioksidia niinkin alhaisessa paineessa kuin 100 mbar. Kaiken kaikkiaan tulokseni osoittavat, että vetyä tuottavien syanobakteerien sopeutuminen erilaisiin stressioloihin vaihtelee kannasta riippuen. Syvällinen ymmärrys syanobakteerien stressivasteista on erityisen tärkeää, kun suunnitellaan teolliseen tuotantoon tähtääviä syanobakteerisovelluksia

The effect of previous obstetric interventions in the outcome of placenta previa

Background: Increase in the incidence of prior caesarean section and other obstetric interventions have contributed to a rise in the number of pregnancies complicated by placenta previa and its associated adverse maternal and perinatal outcome. This study compared the incidence of placenta previa, associated risk factors, placental position, complications and feto-maternal outcome in scarred and unscarred uterus. Objective of present study was to compare the antepartum, intrapartum and postpartum complications in placenta previa between previously scarred uterus and unscarred uterus.Methods: This was a prospective “nested” case control study for a period of 18 months, conducted at SAT Hospital, Medical College, Thiruvananthapuram with diagnosed cases of placenta previa with previously scarred uterus and without a previously scarred uterus. Statistical method used for analysis was chi-square test and students test wherever appropriate. P<0.05 was taken as significant.Results: In this study of 242 patients, there were 134 in the case group and 108 in the control group. The major types of previa were seen in the previously scarred uterus compared to unscarred uterus (55.9% versus 37.9%). Occurrence of recurrent APH (58.9% Vs 41.6%), postpartum haemorrhage (69.4% Vs 48.1%), adherent placenta (5.9% versus 0%) and need for additional operative procedures (66.4% versus 53.7%) including obstetric hysterectomy, need for blood transfusions, postoperative complications (9.7% versus 1.8%), long postoperative hospital stay were all significantly associated with cases of placenta previa in previously scarred uterus.Conclusions: The primary caesarean rate needs to be reduced in order to reduce future pregnancy problems like adherent placenta and caesarean hysterectomy. Such patients need early referral and management in a tertiary health centre with all facilities available for a better maternal and neonatal outcome

Risk factors for perinatal mortality: a case control study from Thiruvananthapuram, Kerala, India

Background: The greatest risks to life are in its very beginning. Although a good start in life begins well before birth, it is just before, during, and in the very first hours and days after birth that life is most at risk. This prospective case control study was designed on maternal risk factors for perinatal mortality.Methods: This was a case control study conducted in the Department of Obstetrics and Gynecology and Department of Paediatrics, Medical College Trivandrum for one year period in 2004-2005. The cases were all the fresh and macerated still births and early neonatal death cases during the study period. The controls were chosen as the next delivery entry in the OR register.Results: During this period, the total number of deliveries was 14,796 and there were 431 perinatal deaths. The perinatal mortality rate was 29.12. This was much higher compared to Kerala’s perinatal mortality rate of 10, the reason being that the study is conducted in a tertiary referral hospital with one of the best new born care nurseries and a large number of referrals. The most significant risk factors for perinatal mortality were low socio-economic status, referrals, late registration, prematurity, low birth weight, intra-uterine growth restriction, maternal diseases like gestational hypertension and gestational diabetes and intrapartum complications like abruption.Conclusions: Perinatal mortality rate serves as the most sensitive index of maternal and neonatal care. Good antenatal care and prevention of preterm birth may play a key role in further reduction of PMR

Obstetric outcome in twin gestation with reference to chorionicity

Background: Monochorionic twin pregnancies are at greater risk for growth abnormalities and other complications. This study aims to outline the obstetric problems faced by twins in general and also to determine the influence of chorionicity on pregnancy and perinatal outcome in twins. Objective of present study was to compare the obstetric and perinatal outcome between monochorionic and dichorionic twins.Methods: A clinical non-interventional prospective observational study was conducted in a tertiary care hospital over a period of 1 year. 232cases of twin pregnancies were followed up from first trimester. The antepartum complications, mode of delivery, presentation, pregnancy outcome, condition of babies and perinatal mortality were compared between mono-chorionic and dichorionic twins.Results: Among 232 cases of twins studied, 2/3rd were dichorionic and 1/3rd were monochorionic. The mean gestational age for Monochorionic (MC) twins was 33.2 weeks whereas it was 35.6 weeks for Dichorionic (DC) twins. Preterm delivery was significantly associated with mono-chorionicity. Elective CS was done more for MC twins compared to DC twins. The mean birth weight of MC twins was 1.7 kg compared to 2.1 kg among DC twins. Low APGAR scores were seen in 31.3% of MC twins compared to 15.8% of DC twins. The number of asphyxiated babies (12.5%), stillborn (7.5%) and macerated babies (10%) were more in MC group in comparison to DC group where it was (9.9%, 2.1%, 0.7%) respectively. Risk of IBN admissions were more in MC than DC twins. (31.3% Vs 21.1%) Adverse perinatal outcome was associated more with MC pregnancies (37.5%) than DC. (11.8%).Conclusions: Mono-chorioncity was significantly associated with pregnancy complications and adverse perinatal outcome. Hence early diagnosis of chorionicity and referral to a tertiary centre with fetal medicine unit and newborn care is very important in reducing morbidity and perinatal mortality among MC twins

Energy efficient anti-collision algorithm for the RFID networks

Energy efficiency is crucial for radio frequency identification (RFID) systems as the readers are often battery operated. The main source of the energy wastage is the collision which happens when tags access the communication medium at the same time. Thus, an efficient anti-collision protocol could minimize the energy wastage and prolong the lifetime of the RFID systems. In this regard, EPCGlobal-Class1-Generation2 (EPC-C1G2) protocol is currently being used in the commercial RFID readers to provide fast tag identification through efficient collision arbitration using the Q algorithm. However, this protocol requires a lot of control message overheads for its operation. Thus, a reinforcement learning based anti-collision protocol (RL-DFSA) is proposed to provide better time system efficiency while being energy efficient through the minimization of control message overheads. The proposed RL-DFSA was evaluated through extensive simulations and compared with the variants of EPC-Class 1 Generation 2 algorithms that are currently being used in the commercial readers. The results show conclusively that the proposed RL-DFSA performs identically to the very efficient EPC-C1G2 protocol in terms of time system efficiency but readily outperforms the compared protocol in the number of control message overhead required for the operation

Evaluation of light energy to H2 energy conversion efficiency in thin films of cyanobacteria and green alga under photoautotrophic conditions

Cyanobacteria and green algae harness solar energy to split water and to fix CO2. Under specific conditions, they are capable of photoproduction of molecular hydrogen (H2). This study compares the light-energy-to-hydrogen-energy conversion efficiency (LHCE) in two heterocystous, N2-fixing cyanobacteria (wild-type Calothrix sp. strain 336/3 and the δhupL mutant of Anabaena sp. strain PCC 7120) and in the sulfur-deprived green alga, Chlamydomonas reinhardtii strain CC-124, after entrapment of the cells in thin Ca2+-alginate films. The experiments, performed under photoautotrophic conditions, showed higher LHCEs in the cyanobacteria as compared to the green alga. The highest efficiency of ca. 2.5% was obtained in films of the entrapped δhupL strain under low light condition (2.9Wm-2). Calothrix sp. 336/3 films produced H2with a maximum efficiency of 0.6% under 2.9Wm-2, while C. reinhardtii films produced H2most efficiently under moderate light (0.14% at 12.1Wm-2). Exposure of the films to light above 16Wm-2led to noticeable oxidative stress in all three strains, which increased with light intensity. The presence of oxidative stress was confirmed by increased (i) degradation of chlorophylls and some structural carotenoids (such as β-carotene), (ii) production of hydroxylated carotenoids (such as zeaxanthin), and (iii) carbonylation of proteins. We conclude that the H2photoproduction efficiency in immobilized algae and cyanobacteria can be further improved by entrapping cultures in immobilization matrices with increased permeability for gases, especially oxygen, while matrices with low porosity produced increased amounts of xanthophylls and other antioxidant compounds.</p

Carotenoid Biosynthesis in Calothrix sp. 336/3: Composition of Carotenoids on Full Medium, During Diazotrophic Growth and After Long-Term H2 Photoproduction

The carotenoid composition of the filamentous heterocystous N2-fixing cyanobacterium Calothrix sp. 336/3 was investigated under three conditions: in full medium (non-diazotrophic growth); in the absence of combined nitrogen (diazotrophic growth); and after long-term H2 photoproduction (diazotrophic medium and absence of nitrogen in atmosphere). Anabaena sp. PCC 7120 and its DeltahupL mutant with disrupted uptake hydrogenase were used as reference strains. Analysis of identified carotenoids and enzymes involved in carotenogenesis showed the presence of three distinct biosynthetic pathways in Calothrix sp. 336/3. The first one is directed towards biosynthesis of myxoxanthophylls, such as myxol 2'-methylpentoside and 2-hydroxymyxol 2'-methylpentoside. The second pathway results in production of hydroxylated carotenoids, such as zeaxanthin, caloxanthin and nostoxanthin, and the last pathway is responsible for biosynthesis of echinenone and hydroxylated forms of ketocarotenoids, such as 3'-hydroxyechinenone and adonixanthin. We found that carotenogenesis in filamentous heterocystous cyanobacteria varies depending on the nitrogen status of the cultures, with significant accumulation of echinenone during diazotrophic growth at the expense of beta-carotene. Under the severe N-deficiency and high CO2 supply, which leads to efficient H2 photoproduction, cyanobacteria degrade echinenone and beta-carotene and accumulate glycosylated and hydroxylated carotenoids, such as myxol (or ketomyxol) 2'- methylpentosides, 3'-hydroxyechinenone and zeaxanthin. We suggest that the stability of the photosynthetic apparatus in Calothrix sp. 336/3 cells under N-deficiency and high carbon conditions, which is also appeared as the partial recovery of the pigment composition by the end of the long-term ( approximately 1 month) H2 photoproduction process, might be mediated by a high content of hydroxycarotenoids.</p

Climate change, extreme events and mental health in the Pacific region

Purpose: This paper aims to address a gap in investigating specific impacts of climate change on mental health in the Pacific region, a region prone to extreme events. This paper reports on a study on the connections between climate change, public health, extreme weather and climate events (EWEs), livelihoods and mental health, focusing on the Pacific region Islands countries. Design/methodology/approach: This paper deploys two main methods. The first is a bibliometric analysis to understand the state of the literature. For example, the input data for term co-occurrence analysis using VOSviewer is bibliometric data of publications downloaded from Scopus. The second method describes case studies, which outline some of the EWEs the region has faced, which have also impacted mental health. Findings: The results suggest that the increased frequency of EWEs in the region contributes to a greater incidence of mental health problems. These, in turn, are associated with a relatively low level of resilience and greater vulnerability. The findings illustrate the need for improvements in the public health systems of Pacific nations so that they are in a better position to cope with the pressures posed by a changing environment. Originality/value: This paper contributes to the current literature by identifying the links between climate change, extreme events, environmental health and mental health consequences in the Pacific Region. It calls for greater awareness of the subject matter of mental health among public health professionals so that they may be better able to recognise the symptoms and relate them to their climate-related causes and co-determinant factors

Correlations between life-detection techniques and implications for sampling site selection in planetary analog missions

We conducted an analog sampling expedition under simulated mission constraints to areas dominated by basaltic tephra of the Eldfell and Fimmvörðuháls lava fields (Iceland). Sites were selected to be “homogeneous” at a coarse remote sensing resolution (10–100 m) in apparent color, morphology, moisture, and grain size, with best-effort realism in numbers of locations and replicates. Three different biomarker assays (counting of nucleic-acid-stained cells via fluorescent microscopy, a luciferin/luciferase assay for adenosine triphosphate, and quantitative polymerase chain reaction (qPCR) to detect DNA associated with bacteria, archaea, and fungi) were characterized at four nested spatial scales (1 m, 10 m, 100 m, and >1 km) by using five common metrics for sample site representativeness (sample mean variance, group F tests, pairwise t tests, and the distribution-free rank sum H and u tests). Correlations between all assays were characterized with Spearman's rank test. The bioluminescence assay showed the most variance across the sites, followed by qPCR for bacterial and archaeal DNA; these results could not be considered representative at the finest resolution tested (1 m). Cell concentration and fungal DNA also had significant local variation, but they were homogeneous over scales of >1 km. These results show that the selection of life detection assays and the number, distribution, and location of sampling sites in a low biomass environment with limited a priori characterization can yield both contrasting and complementary results, and that their interdependence must be given due consideration to maximize science return in future biomarker sampling expeditions

Multiple Different Defense Mechanisms Are Activated in the Young Transgenic Tobacco Plants Which Express the Full Length Genome of the Tobacco Mosaic Virus, and Are Resistant against this Virus

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