Transport genes and chemotaxis in Laribacter hongkongensis: a genome-wide analysis

Background

Laribacter hongkongensis is a Gram-negative, sea gull-shaped rod associated with community-acquired gastroenteritis. The bacterium has been found in diverse freshwater environments including fish, frogs and drinking water reservoirs. Using the complete genome sequence data of L. hongkongensis, we performed a comprehensive analysis of putative transport-related genes and genes related to chemotaxis, motility and quorum sensing, which may help the bacterium adapt to the changing environments and combat harmful substances.

Results

A genome-wide analysis using Transport Classification Database TCDB, similarity and keyword searches revealed the presence of a large diversity of transporters (n = 457) and genes related to chemotaxis (n = 52) and flagellar biosynthesis (n = 40) in the L. hongkongensis genome. The transporters included those from all seven major transporter categories, which may allow the uptake of essential nutrients or ions, and extrusion of metabolic end products and hazardous substances. L. hongkongensis is unique among closely related members of Neisseriaceae family in possessing higher number of proteins related to transport of ammonium, urea and dicarboxylate, which may reflect the importance of nitrogen and dicarboxylate metabolism in this assacharolytic bacterium. Structural modeling of two C⁴-dicarboxylate transporters showed that they possessed similar structures to the determined structures of other DctP-TRAP transporters, with one having an unusual disulfide bond. Diverse mechanisms for iron transport, including hemin transporters for iron acquisition from host proteins, were also identified. In addition to the chemotaxis and flagella-related genes, the L. hongkongensis genome also contained two copies of qseB/qseC homologues of the AI-3 quorum sensing system.

Conclusions

The large number of diverse transporters and genes involved in chemotaxis, motility and quorum sensing suggested that the bacterium may utilize a complex system to adapt to different environments. Structural modeling will provide useful insights on the transporters in L. hongkongensis.     

Seasonal ammonium uptake kinetics of four brown macroalgae: Implications for use in integrated multi-trophic aquaculture

Journal of Applied Phycology - The combined culture of fed species (bivalves, fish) and macroalgae, known as integrated multi-trophic aquaculture (IMTA), has been suggested as a method of...     

Phenotypic responses to temperature in the ciliate Tetrahymena thermophila

Understanding the effects of temperature on ecological and evolutionary processes is crucial for generating future climate adaptation scenarios. Using experimental evolution, we evolved the model ciliate Tetrahymena thermophila in an initially novel high temperature environment for more than 35 generations, closely monitoring population dynamics and morphological changes. We observed initially long lag phases in the high temperature environment that over about 26 generations reduced to no lag phase, a strong reduction in cell size and modifications in cell shape at high temperature. When exposing the adapted populations to their original temperature, most phenotypic traits returned to the observed levels in the ancestral populations, indicating phenotypic plasticity is an important component of this species thermal stress response. However, persistent changes in cell size were detected, indicating possible costs related to the adaptation process. Exploring the molecular basis of thermal adaptation will help clarify the mechanisms driving these phenotypic responses.     

Adjustments in fatty acid composition is a mechanism that can explain resilience to marine heatwaves and future ocean conditions in the habitat‐forming seaweed Phyllospora comosa (Labillardière) C.Agardh

Marine heatwaves are extreme events that can have profound and lasting impacts on marine species. Field observations have shown seaweeds to be highly susceptible to marine heatwaves, but the physiological drivers of this susceptibility are poorly understood. Furthermore, the effects of marine heatwaves in conjunction with ocean warming and acidification are yet to be investigated. To address this knowledge gap, we conducted a laboratory culture experiment in which we tested the growth and physiological responses of Phyllospora comosa juveniles from the southern extent of its range (43–31°S) to marine heatwaves, ocean warming and acidification. We used a ‘collapsed factorial design’ in which marine heatwaves were superimposed on current (today's pH and temperature) and future (pH and temperature projected by 2100) ocean conditions. Responses were tested both during the heatwaves, and after a 7‐day recovery period. Heatwaves reduced net photosynthetic rates in both current and future conditions, while respiration rates were elevated under heatwaves in the current conditions only. Following the recovery period, there was little evidence of heatwaves having lasting negative effects on growth, photosynthesis or respiration. Exposure to heatwaves, future ocean conditions or both caused an increase in the degree of saturation of fatty acids. This adjustment may have counteracted negative effects of elevated temperatures by decreasing membrane fluidity, which increases at higher temperatures. Furthermore, P. comosa appeared to down‐regulate the energetically expensive carbon dioxide concentrating mechanism in the future conditions with a reduction in δ¹³C values detected in these treatments. Any saved energy arising from this down‐regulation was not invested in growth and was likely invested in the adjustment of fatty acid composition. This adjustment is a mechanism by which P. comosa and other seaweeds may tolerate the negative effects of ocean warming and marine heatwaves through benefits arising from ocean acidification.     

Local interleukin-10 production during respiratory syncytial virus bronchiolitis is associated with post-bronchiolitis wheeze

Background

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Following RSV bronchiolitis, 50% of children develop post-bronchiolitis wheeze (PBW). Animal studies have suggested that interleukin (IL)-10 plays a critical role in the pathogenesis of RSV bronchiolitis and subsequent airway hyperresponsiveness. Previously, we showed that ex vivo monocyte IL-10 production is a predictor of PBW. Additionally, heterozygosity of the single-nucleotide polymorphism (SNP) rs1800872 in the IL10 promoter region was associated with protection against RSV bronchiolitis.

Methods

This study aimed to determine the in vivo role of IL-10 in RSV pathogenesis and recurrent wheeze in a new cohort of 235 infants hospitalized for RSV bronchiolitis. IL-10 levels in nasopharyngeal aspirates (NPAs) were measured at the time of hospitalization and the IL10 SNP rs1800872 genotype was determined. Follow-up data were available for 185 children (79%).

Results

Local IL-10 levels during RSV infection turned out to be higher in infants that later developed physician diagnosed PBW as compared to infants without PBW in the first year after RSV infection (958 vs 692 pg/ml, p = 0.02). The IL10 promoter SNP rs1800872 was not associated with IL-10 concentration in NPAs.

Conclusion

The relationship between high local IL-10 levels during the initial RSV infection and physician diagnosed PBW provides further evidence of the importance of the IL-10 response during RSV bronchiolitis.     

UV-B radiation induces changes in polyamine metabolism in the red seaweed <Emphasis Type="Italic">Porphyra cinnamomea</Emphasis>

Early investigations on the productivity of intertidal seaweeds found that, unlike some seaweeds, members of the genus Porphyra, a Rhodophyte, could tolerate physical stressors such as ultraviolet-B radiation (UV-B) both during immersion and when exposed to air. Increased stress tolerance was thought to be due to an unknown mechanism that operated at the thylakoid level. As recent research has shown that polyamines (PAs), bound to the thylakoid membranes of chloroplasts, play a critical role in protecting the photosynthetic apparatus from high-light and UV damage in both higher plants and in unicellular algae, we investigated PA metabolism in Porphyra cinnamomea exposed to UV-B. Our results show that PA biosynthesis was significantly upregulated in P. cinnamomea in response to UV-B, with the greatest proportional increases being in bound soluble putrescine (PUT), which increased by over 200%, in bound soluble spermidine (SPD) and spermine (SPM) which both increased by more than 150% and in bound insoluble SPM which increased by more than 120%. As PAs can be synthesised from ornithine via ornithine decarboxylase (ODC) or from arginine via arginine decarboxylase (ADC) we investigated the pathway via which polyamines were synthesised in P. cinnamomea. While exposure to UV-B caused increases in the activities of both ADC and ODC, the increase in ADC activity was 10 fold greater than that of ODC, suggesting that the ADC pathway was the principle route by which PA levels increased in response to UV-B. Mechanisms of PA mediated UV-B protection are discussed.     

VARIATIONS IN GROWTH,EROSION, PRODUCTIVITY,AND MORPHOLOGY OF ECKLONIA RADIATA (ALARIACEAE; LAMINARIALES) ALONG A FJORD IN SOUTHERN NEW ZEALAND1

Spatial and temporal patterns of growth, erosion, productivity, and morphology of the dominant habitat‐forming kelp Ecklonia radiata (C. Agardh) J. Agardh were studied bimonthly over 1.5 years in a southern New Zealand fjord characterized by strong gradients in light and wave exposure. Spatial differences in growth were observed with rates at two outer coast, high‐light, wave‐exposed sites reaching 0.42 and 0.45 cm · d^?1, respectively, compared to 0.27 cm · d^?1 at an inner, more homogeneous site. Sporophyte productivity was similar among sites, although population productivity was greater at the outer sites due to population density being 5‐fold greater than at the inner site. It was expected that the inner site would have no pronounced seasonal pattern in growth and productivity due to its homogeneity; however, all three sites displayed maximum rates in late winter/spring and minimal in autumn. Growth rates were 2‐fold greater during the first growth period than the following year. This discrepancy was not correlated to inorganic nitrogen (N) levels, which remained low year‐round (<4 μM), and is likely a result of an interaction between light and temperature, and the photosynthetic capability of E. radiata. Variable pigment content indicated photoacclimation at the inner site. Morphological differences were observed between sites, with E. radiata from the inner site having longer, wider, thinner blades and longer stipes. While E. radiata displayed spatial differences in growth, erosion, productivity, and morphology, populations displayed no temporal differences. These results highlight the need for greater understanding of the mechanisms influencing kelp growth and productivity in a unique marine environment.     

The iron-regulated surface proteins IsdA, IsdB, and IsdH are not required for heme iron utilization in Staphylococcus aureus

The iron-regulated surface determinant proteins (Isd) of Staphylococcus aureus are expressed during iron limitation and have been proposed to be involved in the scavenging of iron from heme. In this study, the genes encoding the surface proteins IsdA, IsdB, and IsdH were inactivated in order to determine their combined role. The triple mutant was found to have no defect in growth under any conditions of iron limitation tested. Also using a mouse septic arthritis model of S.?aureus systemic disease, no significant difference in bacterial load was observed for the triple mutant, compared with its otherwise isogenic parent.     

Proteoglycans of uterine fibroids and keloid scars: similarity in their proteoglycan composition

Fibrosis is the formation of excess and abnormal fibrous connective tissue as a result of either a reparative or reactive process. A defining feature of connective tissue is its extracellular matrix, which provides structural support and also influences cellular activity. Two common human conditions that result from fibrosis are uterine fibroids (leiomyomas) and keloid scars. Because these conditions share a number of similarities and because their growth is due primarily to excessive extracellular matrix deposition, we compared the proteoglycans of uterine fibroids and keloid scars with corresponding normal tissues. Our analysis indicates that uterine fibroids and keloid scars contain higher amounts of glycosaminoglycans relative to normal myometrium and normal adult skin respectively. Proteoglycan composition is also different in the fibrotic tissues. Compared with unaffected tissues, uterine fibroids and keloid scars contain higher relative amounts of versican and lower relative amounts of decorin. There is also evidence for a higher level of versican catabolism in the fibrotic tissues compared with unaffected tissues. These qualitative and quantitative proteoglycan differences may play a role in the expansion of these fibroses and in their excessive matrix deposition and matrix disorganization, due to effects on cell proliferation, TGF (transforming growth factor)-β signalling and/or collagen fibril formation.