Host-finding behaviour and navigation capabilities of symbiotic zooxanthellae

Past studies have shown that the initiation of symbiosis between the Red-Sea soft coral Heteroxenia fuscescens and its symbiotic dinoflagellates occurs due to the chemical attraction of the motile algal cells to substances emanating from the coral polyps. However, the resulting swimming patterns of zooxanthellae have not been previously studied. This work examined algal swimming behaviour, host location and navigation capabilities under four conditions: (1) still water, (2) in still water with waterborne host attractants, (3) in flowing water, and (4) in flow with host attractants. Algae were capable of actively and effectively locating their host in still water as well as in flow. When in water containing host attractants, swimming became slower, motion patterns straighter and the direction of motion was mainly towards the host—even if this meant advancing upstream against flow velocities of up to 0.5 mm s⁻¹. Coral-algae encounter probability decreased the further downstream of the host algae were located, probably due to diffusion of the chemical signal. The results show how the chemoreceptive zooxanthellae modify their swimming pattern, direction, velocity, circuity and turning rate to accommodate efficient navigation in changing environmental conditions.     

Coevolution of symbiotic mutualists and parasites in a community context

Recent advances in our knowledge of parasitic and mutualistic associations have confirmed the central role of coevolutionary interactions in population and community ecology. Here, we discuss the potential coevolutionary interdependence of the strength and specificity of symbiotic interactions with the complexity and productivity of their environment. We predict that interactions become less beneficial with increasing environmental quality and that the association of productivity with symbiont specificity depends on the relative strengths of tradeoffs between host range and other life-history parameters. However, as biotic complexity increases, pathogen specificity is predicted to decline, whereas mutualist specificity will increase. Testing these predictions on a geographical scale would contribute significantly to the predictive science of coevolution, and to our ability to manage biological interactions embedded in increasingly fragmented landscapes.     

From cooperation to combat: adverse effect of thermal stress in a symbiotic coral-crustacean community

Although mutualisms are ubiquitous in nature, our understanding of the potential impacts of climate change on these important ecological interactions is deficient. Here, we report on a thermal stress-related shift from cooperation to antagonism between members of a mutualistic coral-dwelling community. Increased mortality of coral-defending crustacean symbionts Trapezia cymodoce (coral crab) and Alpheus lottini (snapping shrimp) was observed in response to experimentally elevated temperatures and reduced coral-host (Pocillopora damicornis) condition. However, strong differential numerical effects occurred among crustaceans as a function of species and sex, with shrimp (75 %), and female crabs (55 %), exhibiting the fastest and greatest declines in numbers. These declines were due to forceful eviction from the coral-host by male crabs. Furthermore, surviving female crabs were impacted by a dramatic decline (85 %) in egg production, which could have deleterious consequences for population sustainability. Our results suggest that elevated temperature switches the fundamental nature of this interaction from cooperation to competition, leading to asymmetrical effects on species and/or sexes. Our study illustrates the importance of evaluating not only individual responses to climate change, but also potentially fragile interactions within and among susceptible species.     

Construction of an artificial symbiotic community using a Chlorella-symbiont association as a model.

Chlorella sorokiniana IAM C-212 produces a polysaccharide gel, termed a sheath, under photoautotrophic conditions. The C. sorokiniana sheath is a suitable habitat for several symbiotic microorganisms because it ensures close proximity between the C. sorokiniana and symbionts. In this study, we established a method for increasing the volume of the sheath produced by C. sorokiniana, and proposed a method for constructing artificial communities of Chlorella and symbiotic microorganisms. The C. sorokiniana sheath was increased by addition of calcium chloride solution. The sheath resulted in coflocculation of C. sorokiniana and the associated symbiotic bacteria, thus strengthening the bacterial-Chlorella symbiotic association. An application of this technique was demonstrated by constructing a complex of C. sorokiniana and a propionate-degrading bacterium (PDS1). Although propionate inhibited the growth of axenic C. sorokiniana, the C. sorokiniana-PDS1 complex showed good growth in a medium containing a high concentration of propionate.     

Construction of an artificial symbiotic community using a Chlorella–symbiont association as a model

Chlorella sorokiniana IAM C-212 produces a polysaccharide gel, termed a sheath, under photoautotrophic conditions. The C. sorokiniana sheath is a suitable habitat for several symbiotic microorganisms because it ensures close proximity between the C. sorokiniana and symbionts. In this study, we established a method for increasing the volume of the sheath produced by C. sorokiniana , and proposed a method for constructing artificial communities of Chlorella and symbiotic microorganisms. The C. sorokiniana sheath was increased by addition of calcium chloride solution. The sheath resulted in coflocculation of C. sorokiniana and the associated symbiotic bacteria, thus strengthening the bacterial– Chlorella symbiotic association. An application of this technique was demonstrated by constructing a complex of C. sorokiniana and a propionate-degrading bacterium (PDS1). Although propionate inhibited the growth of axenic C. sorokiniana , the C. sorokiniana –PDS1 complex showed good growth in a medium containing a high concentration of propionate.     

Psychological and stabilographic features of healthy persons with different capabilities of performing dual tasks

A dual task study including control of postural balance and counting was conducted on 40 healthy subjects (with an average age of 29.8 ± 2.47 years) along with a psychological examination that included estimation of the working memory, attention, and the time of attention switch. Three types of dual task performance were observed: worsening of either one or both components of the dual task, improvement of one component, and improvement of both components of the dual task. 30% of participants performed a dual task better than isolated tasks. Successful performance in the dual task correlated with the higher volume of spatial and working memory, attention, and a rapid switch of attention. The speed of sway of the center of pressure (CoP) negatively correlated with the speed of attention switch, while the amplitude of the CoP shift in the frontal plane negatively correlated with the volume of spatial and working memory. These data suggest involvement of the cognitive resources in controlling the upright balance and a high degree of motor automatism when the dual tasks are successfully performed. Our experimental paradigm is expected to be helpful in predicting individual performance in situations with high information loads.     

景感生态学视角下的健康社区构建

景感生态学是基于中国传统人居环境营造理论与实践结合现代生态学基本原理形成的新兴学科,注重探讨生态系统服务与可持续发展的关系。可持续发展目标中健康与福祉是其重要内容,因此健康人居环境的营造也是景感生态学的重要应用领域之一。在健康人居环境的营造过程中,健康社区构建具有作为"细胞工程"的基础性作用。因此,从景感生态学的视角探讨健康社区的构建,有助于景感生态学进一步应用于可持续发展与人居环境营造的实践,为健康与福祉的顺利实现提供支撑。从健康社区的定义和主要理念出发,基于健康社区构建的需求本体和供给客体及其相互作用关系,结合生态环境科学的"时-空-量-序"的视角,探讨了生态环境研究应用于健康社区构建的作用及面临的系统性不足、人文性不足和耦合性不足等挑战;进而以景感生态学作为连接生态环境学科与建筑规划学科的纽带,探讨了景感生态学在应对上述挑战中的作用。从景感生态学视角来看,健康社区构建就是将人类健康这一愿景融入到社区健康需求本体与健康供给客体及其相互关系的调控与营造,从而实现社区及人群的健康和可持续发展。健康社区的构建强调社区人群主观健康需求与客观健康供给之间的互动与耦合,与景感生态学强调"景"与...     

Fungi inhabiting the healthy human gastrointestinal tract: a diverse and dynamic community

Fungal DNA was selectively amplified, and the ITS region sequenced, from fecal samples taken from 45 healthy human volunteers at one (21 volunteers) or two (24 volunteers) time points. Seventy-two operational taxonomic units, representing two phyla and ten classes of fungi, were recovered. Candida yeasts, notably Candida tropicalis (present in 51 samples), and yeasts in the Dipodascaceae (39 samples), dominated, while 38 OTUs were detected in a single sample each. Fungi included known human symbionts (Candida, Cryptococcus, Malassezia and Trichosporon spp.), common airborne fungi (Cladosporium sp.) and fungi known to be associated with food (Debaryomyces hansenii and high salt fermented foods; Penicillium roqueforti and blue cheese). In contrast with gut-associated bacteria, fungi occurred in much lower abundance and diversity, and fungal composition appeared unstable over time.     

Ectomychorrizal DB: a symbiotic association database

Ectomycorrhizal (ECM) fungal species, a "Symbiotic" relationship between tress and fungi in forest has a great ecological and economic importance. Here is an attempt to describe database named "EctomycorrhizalDB", addressing ECM diversity of Central Himalaya (Kumaun region), with special emphasis on their characterization, physical properties and morphological features along with specifications. This database would help the scientific community to draw a better understanding of the environmental factors that affects species diversity. AVAILABILITY: The database is available for free at http://www.kubic.nic.in/ectomychorhiza.     

SIGNing a symbiotic treaty with gut microbiota

Beneficial microbes hold great promise for the treatment of a wide range of immune and inflammatory disorders. In this issue of The EMBO Journal, Lightfoot and colleagues report how the food‐grade bacterium Lactobacillus acidophilus helps the immune system to limit experimental colitis in mice through interaction between SIGNR3 and surface layer protein A (SlpA) in L. acidophilus. These results pave the way for future development of novel therapies for inflammatory diseases, including inflammatory bowel disease.     

Improvement of Kefir yeast by mutation with N-methyl-N- nitrosoguanidine

A commercial culture of Kefir grew well at 30°C and 37°C with NaCl up to 4% (w/v) but at 42°C and 4% (w/v) NaCl it grew very slowly. These conditions were selected for the mutation with N-methyl-N-nitrosoguanidine in order to improve cell yield at high temperatures and salt concentration. The mutated cells had higher biomass and growth rate compared with the original culture. The improvement of Kefir at high temperatures and salt concentrations offers advantages for uses in single cell protein production and alcohol production from whey containing high salt.     

Repopulation of a sea anemone with symbiotic dinoflagellates: Analysis by in vivo fluorescence

Individuals in a population of aposymbiotic Aiptasia pulchella Carlgren were each inoculated with homologous zooxanthellae. The rate of repopulation of the anemones (i.e. the in situ growth rate of the zooxanthellae) was determined non-destructively from the mean in vivo fluorescence per anemone over 19 days. As zooxanthellae cell density increased, chlorophyll a per cell increased, but fluorescence per cell decreased, probably as a result of self-shading. The emergent relationship between in vivo fluorescence and number of zooxanthellae was linear over the range of cell densities investigated. The-specific growth rate during exponential growth was 0.4·day⁻¹ between days 7 and 15. As repopulation approached saturation (ca. 0.5 × 10⁶ cells per mg animal soluble protein) at about 19 days, the growth rate decreased and approached the steady state growth rate of about 0.02 · day⁻¹ of normal symbiotic anemones. Rates of repopulation of A. pulchella by freshly isolated and cultured homologous zooxanthellae were virtually identical.     

The nucleolus: an old factory with unexpected capabilities

The function of the nucleolus as a factory for assembling ribosomal subunits is well established, but many unrelated activities have been discovered over the past decade. Our understanding of the dynamics of nucleolar structure and its reassembly at the end of mitosis has recently advanced and the small nucleolar RNAs have been shown to be major players in the processing and modification of preribosomal RNA. Unexpectedly, the nucleolus also seems to play a role in nuclear export, sequestering regulatory molecules, modifying small RNAs, assembling ribonucleoprotein (RNP) and controlling aging.     

外生菌根真菌与内生细菌共生互作的研究进展

外生菌根真菌能与很多高等植物共生,广泛存在于自然界,在促进植物生长和养分吸收、增强宿主抗逆性及维持森林生态系统稳定等方面发挥着重要作用。除与寄主植物密切联系外,外生菌根真菌,在其生命周期中与细菌群落进行物理和代谢相互作用常形成共生关系。这些细菌对外生菌根真菌菌丝生长、生物量增加及子实体的形成具有积极影响。本文阐述了外生菌根真菌与内生细菌共生现象的发现、共生关系的建立、内生细菌促进外生菌根真菌生长和发育及宿主与微生物组的研究方法等,以期更好地巩固外生菌根真菌的生物学及生态学等基础性知识,并利用细菌与真菌的相互作用为可食用外生菌根真菌的生物防治、菌肥研究、人工驯化及栽培提供思路。     

Kefir alleviates obesity and hepatic steatosis in high-fat diet-fed mice by modulation of gut microbiota and mycobiota: targeted and untargeted community analysis with correlation of biomarkers

Kefir is a probiotic beverage containing over 50 species of lactic acid bacteria and yeast. In this study, the anti-obesity and anti-non-alcoholic fatty liver disease (NAFLD) effects of kefir were comprehensively addressed along with targeted and untargeted community analysis of the fecal microbiota in a high-fat diet (HFD)-induced obese mouse model. HFD-fed C57BL/6 mice were orally administrated either kefir or milk (control) once a day for 12 weeks, and body and organ weight, fecal microbiota and mycobiota, histopathology, blood cholesterol and cytokines and gene expressions were analyzed. Compared to the control, mice in the kefir group exhibited a significantly lower body weight (34.18 g vs. 40.24 g; p=0.00004) and histopathological liver lesion score (1.13 vs. 3.25; p=0.002). Remarkably, the kefir-fed mice also harbored more Lactobacillus/Lactococcus (7.01 vs. 6.32 log CFU/g), total yeast (6.07 vs. 5.01 log CFU/g) and Candida (5.56 vs. 3.88 log CFU/g). Kefir administration also up-regulated genes related to fatty acid oxidation, PPARα and AOX, in both the liver and adipose tissue (PPARα, 2.95- and 2.15-fold; AOX, 1.89- and 1.9-fold, respectively). The plasma concentration of IL-6, a proinflammatory marker, was significantly reduced following kefir consumption (50.39 pg/ml vs. 111.78 pg/ml; p=0.03). Strikingly, the populations of Lactobacillus/Lactococcus, total yeast and Candida were strongly correlated with PPARα gene expression in adipose and hepatic tissue (r=0.599, 0.580 and 0.562, respectively). These data suggest that kefir consumption modulates gut microbiota and mycobiota in HFD-fed mice, which prevents obesity and NAFLD via promoting fatty acid oxidation.     

Saprotrophic capabilities as functional traits to study functional diversity and resilience of ectomycorrhizal community

In an accompanying editorial Dr Petr Baldrian made a case casting doubt on our recent work addressing the saprophytic potential of ectomycorrhizal (EM) fungi. Dr Baldrian’s statements illustrate a very valid truth: the book is still very much open on this subject. The point he raised that the only logical reason for these fungi to be responding to high carbon demand or decreased host photosynthetic capacity by up-regulating enzymes is for the purpose of carbon acquisition is valid as well. Despite this, he makes the case that there is no compelling evidence that EM fungi exhibit saprophytic activity. The concept central to Dr Baldrian’s conclusion is that even though some EM fungi possess the genes necessary for saprophytic behaviour and may even express these genes, EM fungi do not inhabit a position in the soil column that provides access to usable substrate. In this paper we present both previously published and newly obtained data that demonstrate that this assumption is erroneous, and we present arguments that place the saprophytic potential of EM fungi within a broad ecological context.     

Stage correlation of symbiotic bacterial community and function in the development of litchi bugs (Hemiptera: Tessaratomidae)

Bacterial symbionts of insects have been shown to play important roles in host fitness. However, little is known about the bacterial community of Tessaratoma papillosa which is one of the most destructive pests of the well-known fruits Litchi chinensis Sonn and Dimocarpus longan Lour in Oriental Region, especially in South-east Asia and adjacent areas. In this study, we surveyed the bacterial community diversity and dynamics of T. papillosa in all developmental stages with both culture-dependent and culture-independent methods by the third-generation sequencing technology. Five bacterial phyla were identified in seven developmental stages of T. papillosa. Proteobacteria was the dominant phylum and Pantoea was the dominant genus of T. papillosa. The results of alpha and beta diversity analyses showed that egg stage had the most complex bacterial community. Some of different developmental stages showed similarities, which were clustered into three phases: (1) egg stage, (2) early nymph stages (instars 1–3), and (3) late nymph stages (instars 4–5) and adult stage. Functional prediction indicated that the bacterial community played different roles in these three phases. Furthermore, 109 different bacterial strains were isolated and identified from various developmental stages. This study revealed the relationship between the symbiotic bacteria and the development of T. papillosa, and may thus contribute to the biological control techniques of T. papillosa in the future.