Proteins released into the plant apoplast by the obligate parasitic protist Albugo selectively repress phyllosphere-associated bacteria.

Biotic and abiotic interactions shape natural microbial communities. The mechanisms behind microbe-microbe interactions, particularly those protein based, are not well understood. We hypothesize that released proteins with antimicrobial activity are a powerful and highly specific toolset to shape and defend plant niches. We have studied Albugo candida, an obligate plant parasite from the protist Oomycota phylum, for its potential to modulate the growth of bacteria through release of antimicrobial proteins into the apoplast. Amplicon sequencing and network analysis of Albugo-infected and uninfected wild Arabidopsis thaliana samples revealed an abundance of negative correlations between Albugo and other phyllosphere microbes. Analysis of the apoplastic proteome of Albugo-colonized leaves combined with machine learning predictors enabled the selection of antimicrobial candidates for heterologous expression and study of their inhibitory function. We found for three candidate proteins selective antimicrobial activity against Gram-positive bacteria isolated from A. thaliana and demonstrate that these inhibited bacteria are precisely important for the stability of the community structure. We could ascribe the antibacterial activity of the candidates to intrinsically disordered regions and positively correlate it with their net charge. This is the first report of protist proteins with antimicrobial activity under apoplastic conditions that therefore are potential biocontrol tools for targeted manipulation of the microbiome.

Cell specialization in cyanobacterial biofilm development revealed by expression of a cell-surface and extracellular matrix protein.

Cyanobacterial biofilms are ubiquitous and play important roles in diverse environments, yet, understanding of the processes underlying the development of these aggregates is just emerging. Here we report cell specialization in formation of Synechococcus elongatus PCC 7942 biofilms-a hitherto unknown characteristic of cyanobacterial social behavior. We show that only a quarter of the cell population expresses at high levels the four-gene ebfG-operon that is required for biofilm formation. Almost all cells, however, are assembled in the biofilm. Detailed characterization of EbfG4 encoded by this operon revealed cell-surface localization as well as its presence in the biofilm matrix. Moreover, EbfG1-3 were shown to form amyloid structures such as fibrils and are thus likely to contribute to the matrix structure. These data suggest a beneficial 'division of labor' during biofilm formation where only some of the cells allocate resources to produce matrix proteins-'public goods' that support robust biofilm development by the majority of the cells. In addition, previous studies revealed the operation of a self-suppression mechanism that depends on an extracellular inhibitor, which supresses transcription of the ebfG-operon. Here we revealed inhibitor activity at an early growth stage and its gradual accumulation along the exponential growth phase in correlation with cell density. Data, however, do not support a threshold-like phenomenon known for quorum-sensing in heterotrophs. Together, data presented here demonstrate cell specialization and imply density-dependent regulation thereby providing deep insights into cyanobacterial communal behavior.

Predicting Lifestyle from Positive Selection Data and Genome Properties in Oomycetes.

As evidenced in parasitism, host and niche shifts are a source of genomic and phenotypic diversification. Exemplary is a reduction in the core metabolism as parasites adapt to a particular host, while the accessory genome often maintains a high degree of diversification. However, selective pressures acting on the genome of organisms that have undergone recent lifestyle or host changes have not been fully investigated. Here, we developed a comparative genomics approach to study underlying adaptive trends in oomycetes, a eukaryotic phylum with a wide and diverse range of economically important plant and animal parasitic lifestyles. Our analysis reveals converging evolution on biological processes for oomycetes that have similar lifestyles. Moreover, we find that certain functions, in particular carbohydrate metabolism, transport, and signaling, are important for host and environmental adaptation in oomycetes. Given the high correlation between lifestyle and genome properties in our oomycete dataset, together with the known convergent evolution of fungal and oomycete genomes, we developed a model that predicts plant pathogenic lifestyles with high accuracy based on functional annotations. These insights into how selective pressures correlate with lifestyle may be crucial to better understand host/lifestyle shifts and their impact on the genome.

Amyloid Proteins in Plant-Associated Microbial Communities.

Amyloids have proven to be a widespread phenomenon rather than an exception. Many proteins presenting the hallmarks of this characteristic beta sheet-rich folding have been described to date. Particularly common are functional amyloids that play an important role in the promotion of survival and pathogenicity in prokaryotes. Here, we describe important developments in amyloid protein research that relate to microbe-microbe and microbe-host interactions in the plant microbiome. Starting with biofilms, which are a broad strategy for bacterial persistence that is extremely important for plant colonization. Microbes rely on amyloid-based mechanisms to adhere and create a protective coating that shelters them from external stresses and promotes cooperation. Another strategy generally carried out by amyloids is the formation of hydrophobic surface layers. Known as hydrophobins, these proteins coat the aerial hyphae and spores of plant pathogenic fungi, as well as certain bacterial biofilms. They contribute to plant virulence through promoting dissemination and infectivity. Furthermore, antimicrobial activity is an interesting outcome of the amyloid structure that has potential application in medicine and agriculture. There are many known antimicrobial amyloids released by animals and plants; however, those produced by bacteria or fungi remain still largely unknown. Finally, we discuss amyloid proteins with a more indirect mode of action in their host interactions. These include virulence-promoting harpins, signaling transduction that functions through amyloid templating, and root nodule bacteria proteins that promote plant-microbe symbiosis. In summary, amyloids are an interesting paradigm for their many functional mechanisms linked to bacterial survival in plant-associated microbial communities.

Non-capable residents: is the experience of dependence understood in nursing homes? A qualitative study.

OBJECTIVE: The aim of the present study was to describe how dependence was experienced by Spanish nursing home residents with functional limitations. METHODS: A qualitative phenomenological approach was followed. An initial purposeful sampling of Spanish residents in for-profit nursing homes in the southern area of Madrid was carried out. Theoretical sampling was also implemented in order to gain a more in-depth understanding of dependence. The inclusion criteria for nursing home residents were: aged 60 years old or older, having a functional impairment (Barthel Index <90), and lack of any cognitive impairment (Mini-Mental State Examination-Folstein >19) and able to communicate verbally in Spanish. Data were collected using unstructured and semi-structured interviews. The interviews were tape recorded and fully transcribed. Data collection was concluded once theoretical saturation was reached, and the data were analyzed using the Giorgi proposal. RESULTS: A total of 30 residents (15 female and 15 male) with a mean age of 83 years were included. Two main themes that describe the significance of dependence in nursing homes emerged from the data: (i) remaining "capable", with one subtheme named "building the difference", where residents described their own dependence classification of "non-capable" residents; and (ii) "sharing life", with two subthemes named "living together with non-capable residents" and "sharing the environment". Being considered as "non-capable" is labelling the resident forever. CONCLUSIONS: The dependence experience of Spanish nursing home residents might help us gain a deeper insight into their expectations about functional limitations, as well as to understand the change in the relationship between residents considered "non-capable", caregivers and the other residents.

Is the influence of nurse care practices and nursing home organization understood? A qualitative study.

AIM: To describe residents' experience of nursing home organization and nursing care practices in a region of Spain. BACKGROUND: Nursing home organization, nursing practices and rules within the institution may all influence residents' daily living and their perception on the quality of care provided. DESIGN: A qualitative approach was conducted, using purposeful and theoretical sampling. Data were collected from nursing home residents, following unstructured and semi-structured interviews, researcher field notes and residents' personal diaries and letters. Giorgi analysis was conducted. RESULTS: Two main themes emerged. (1) 'Following nursing home rules'. Norms may be seen as boundaries, especially for those residents who were independent before admission. (2) 'Prioritizing nursing care in residents'. Prioritizing the nursing care may limit the autonomy of residents because it does not meet their preferences and needs. CONCLUSION: Understanding the meaning of nursing home organization and nursing care practices with nursing home residents might provide deeper insight into their expectations. IMPLICATIONS FOR NURSING MANAGEMENT: Nursing staff should have greater involvement in the nursing home organization, as well as in prioritizing the care provision based on resident's needs and preferences.

Is the mealtime experience in nursing homes understood? A qualitative study.

AIM: The aim of the present study was to explore the significance of the mealtime experience among residents of nursing homes in Spain. METHODS: A qualitative phenomenological approach was followed. An initial purposeful sampling of Spanish residents in for-profit nursing homes in the southern area of Madrid was carried out. A theoretical sampling was also implemented in order to gain a more in-depth understanding of dependence. Inclusion criteria for nursing home residents were: age (60 years or older) and lack of any cognitive impairment. Data were collected using unstructured and semistructured interviews. Data collection was concluded once theoretical saturation was reached, and the data were analysed using the Giorgi proposal. RESULTS: A total of 26 residents with a mean age of 83 years were included. Three main themes that describe the significance of meals in nursing homes emerged from the data: (i) timing of the meals - mealtimes serve as a point of reference for organizing activities in the nursing home and orient the residents during the day; (ii) table allocation - table allocation depends on the judgment of the personnel, the behavior of each resident and on the input from the residents that use a table; and (iii) the meals themselves - food is experienced as a privilege, as a sign of autonomy and normality, and as an indicator of personal identity. CONCLUSION: Understanding the social significance of meals for residents in nursing homes would provide deeper insight into resident expectations. This will in turn help to improve service and quality of life for residents.