Microbial Ecology最新文献

Microbial biotechnology employs techniques that rely on the natural interactions that occur in ecosystems. Bacteria, including rhizobacteria, play an important role in plant growth, providing crops with an alternative that can mitigate the negative effects of abiotic stress, such as those caused by saline environments, and increase the excessive use of chemical fertilizers. The present study examined the promoting potential of bacterial isolates obtained from the rhizospheric soil and roots of the Asparagus officinalis cultivar UF-157 F2 in Viru, la Libertad, Peru. This region has high soil salinity levels. Seventeen strains were isolated, four of which are major potential plant growth-promoting traits, and were characterized based on their morphological and molecular characteristics. These salt-tolerant bacteria were screened for phosphate solubilization, indole acetic acid, deaminase activity, and molecular characterization by 16S rDNA sequencing. Fifteen samples were from saline soils of A. officinalis plants in the northern coastal desert of San Jose, Lambayeque, Peru. The bacterial isolates were screened in a range of salt tolerances from 3 to 6%. Isolates 05, 08, 09, and 11 presented maximum salt tolerance, ammonium quantification, phosphate solubilization, and IAA production. The four isolates were identified by sequencing the amplified 16S rRNA gene and were found to be Enterobacter sp. 05 (OQ885483), Enterobacter sp. 08 (OQ885484), Pseudomonas sp. 09 (OR398704) and Klebsiella sp. 11 (OR398705). These microorganisms promoted the germination of Zea mays L. plants, increased the germination rates in the treatments with chemical fertilizers at 100% and 50%, and the PGPRs increased the height and length of the roots 40 days after planting. The beneficial effects of salt-tolerant PGPR isolates isolated from saline environments may lead to new species that can be used to overcome the detrimental effects of salt stress on plants. The biochemical response and inoculation of the three isolates prove the potential of these strains as sources of products to develop new compounds, confirming their potential as biofertilizers for saline environments.

Estuarine ecosystems are among the most important natural ecosystems on Earth and contribute substantially to human survival and development. The Yellow River Estuary (YRE) is the second largest estuary in China. Microbial communities play an essential role in the material cycle and energy flow in estuarine ecosystems. To date, our knowledge of the spatial patterns of bacterial and archaeal communities is limited. In this study, we investigated the spatial profile of bacterial and archaeal communities and their co-occurrence patterns, functional roles, and environmental driving factors in the intertidal sediments of the YRE from June to July, 2019. The results showed that Proteobacteria, Bacteroidetes, Chloroflexi, and Planctomycetes were the dominant bacterial phyla, whereas Nanoarchaeaeota, Euryarchaeota and Thaumarchaeota were the dominant archaeal phyla in the intertidal sediments of the YRE. Diversity indices and differential abundance analyses revealed significant (p < 0.05) differences in the bacterial and archaeal communities in the intertidal sediments of the YRE. Bacterial communities demonstrated distinct correlations with heavy metals and pollutants. Six archaeal genera exhibited co-occurrence patterns with bacterial genera. Functions associated with sulfur cycles, disease, and pollution were specific to bacterial communities. This study presents a detailed outline of the spatial patterns of microbial communities in the YRE, enriching our understanding of microbial ecology, especially of bacteria and archaea.

The Añana Salt Valley (northern Spain) is a continental saltern consisting of a series of natural springs that have been used for salt production for at least 7000 years. This habitat has been relatively understudied; therefore, prokaryotic diversity was investigated through Illumina-based 16S rRNA gene sequencing to determine if the waters within the valley exhibit distinctive microbiological characteristics. Two main types of water were found in the valley: salty (approximately 200 g/L salinity) from the diapiric structure and brackish (≤ 20 g/L salinity) from shallow streams. The beta diversity indices showed that salinity was the primary factor influencing the prokaryotic distribution. However, a niche-specific influence was observed between waters of the same origin, with significant differences in the relative abundance of the ASVs. The microbiome of the saltern revealed that the archaeal domain was mainly restricted to salty waters, while the bacterial domain was ubiquitous throughout the saltern, with a notable prevalence in brackish waters. The main bacterial and archaeal phyla identified were Pseudomonadota and Halobacterota, respectively. The genus Halorubrum was abundant and widespread in salty waters, while Pseudomonas was a significant part of the prokaryote community, mainly in brackish waters. The relative abundance of the genera Haloplanus and Salinibacter increased in the salt ponds used for salt production. The taxa involved in chemoheterotrophy and fermentation were widespread, sharing the same niche. Overall, the location of this saltern on a diapiric structure favors the occurrence of waters with different origins that affect the prokaryotic distribution beyond the niche location in the valley.

Temperate estuary wetlands act as natural filters for microbiological contamination and have a profound impact on "One Health." However, knowledge of microbiological ecology security across the different habitats in temperate estuarine wetlands remains limited. This study employed meta-analysis to explore the characteristics of bacterial communities, potential pathogens, and antibiotic resistance genes (ARGs) across three heterogeneous habitats (water, soil, and sediment) within the Liaohe Estuary landscape. The diversity and composition of the three bacterial communities differed with biogeography, temperature, and pH, with the highest α-diversity showing a significantly negative correlation along latitude in soil. Furthermore, aminoglycosides were significantly enriched in water and soil, while dihydrofolate was more likely to be enriched in soil. The potential pathogens, Pseudoalteromonas and Planococcus, were dominant in water and sediment, while Stenotrophomonas was the dominant bacterium in soil. The network topology parameter revealed interspecific interactions within the community. PLS-PM highlights the main direct factors affecting the abundance of potential pathogens and the spread of ARGs, while temperature and pH indirectly influence these potential pathogens. This study advances our understanding of bacterial communities in estuarine wetlands, while highlighting the need for effective monitoring to mitigate the risks associated with potential pathogens and ARGs in these ecosystems.

Posidonia oceanica retains a large amount of carbon within its belowground recalcitrant structure, the 'matte,' which is characterized by low oxygen availability and biodegradation. Fungi may play a pivotal role in carbon sequestration within the matte, even if little/no information is available. To fill this gap, we profiled fungal communities from the upper and lower layers of alive and dead matte, by using an ITS2-5.8S rDNA metabarcoding approach. The study was conducted in a shallow coastal stretch of the Aegean Sea (Crete). Then, 184 operational taxonomic units were identified, predominantly belonging to Ascomycota, in alive and dead matte. Nevertheless, their composition significantly differed: the host-specific Posidoniomyces atricolor was dominant in alive but not in dead matte, while fast-growing saprotrophs, potentially accelerating the decomposition rate, increased in dead matte. These findings lay the groundwork for future investigations on the possible increase of biodegradation under the changing environmental conditions.

Coral thermal tolerance is intimately linked to their symbiotic relationships with photosynthetic microorganisms. However, the potential compensatory role of symbiotic photosynthetic bacteria in supporting Symbiodiniaceae photosynthesis under extreme summer temperatures remains largely unexplored. Here, we examined the seasonal variations in Symbiodiniaceae and photosynthetic bacterial community structures in Pavona decussata corals from Weizhou Island, Beibu Gulf, China, with particular emphasis on the role of photosynthetic bacteria under elevated temperature conditions. Our results revealed that Symbiodiniaceae density and Chlorophyll a concentration were lowest during the summer and highest in the winter. Notably, the summer bacterial community was predominately composed of the proteorhodopsin bacterium BD 1-7 _clade, alongside a significant increase in Cyanobacteria, particularly Synechococcus_CC9902 and Cyanobium_PCC-6307, which represented 61.85% and 31.48% of the total Cyanobacterial community, respectively. In vitro experiments demonstrated that Cyanobacteria significantly enhanced Symbiodiniaceae photosynthetic efficiency under high-temperature conditions. These findings suggest that the increased abundance of photosynthetic bacteria during summer may mitigate the adverse physiological effects of reduced Symbiodiniaceae density, thereby contributing to coral stability. Our study highlights a potential synergistic interaction between Symbiodiniaceae and photosynthetic bacteria, emphasizing the importance of understanding these dynamic interactions in sustaining coral resilience against environmental stress, although further research is necessary to establish their role in preventing coral bleaching.

Plant growth-promoting bacteria (PGPB) are among the most promising alternatives to mineral fertilizers. However, little is known about the effects of applied bacteria on the native microbiota, including the rhizobacterial community, which plays a crucial role in bacteria-plant interactions. Therefore, this study is aimed at assessing the effects of PGPB not only on plants but also, importantly, on the native rhizobacterial community of winter oilseed rape. The bacterial consortium, consisting of Pseudomonas sp. KR227 and Azotobacter PBC1 (P2A), slightly promoted plant growth, increasing the root weight by 21.95% and seed yield by 18.94%. This likely results from its ability to produce indole-3-acetic acid (IAA), solubilize phosphorus, and fix nitrogen, as indicated by a 35.76% increase in N-NH₄ and a 35.05% increase in available phosphorus (AP). The introduced PGPB altered the rhizobacterial community of rapeseed, increasing the relative abundance of the phylum Proteobacteria and the genus Pseudomonas while decreasing the relative abundance of phylum Verrucomicrobiota (3 weeks after inoculation). Moreover, Proteobacteria were positively correlated with AP, while Verrucomicrobiota were correlated with N-NH₄. At the genus level, Flavobacterium and Pseudomonas were positively correlated with AP, whereas Candidatus Udaeobacter showed a positive correlation with N-NH₄ and a negative correlation with pH. Importantly, the P2A consortium did not significantly affect the diversity of native rapeseed rhizobacteria. These findings suggest that the tested P2A consortium has potential as a biostimulant in rapeseed cultivation.

To understand the effects of agricultural land use change and management on soil carbon (C) cycling, it is crucial to examine how these changes can influence microbial soil C cycling. Network analysis can offer insights into the structure, complexity, and stability of the soil microbiome in response to environmental disturbances, including land use change. Using SparCC-based co-occurrence networks, we studied how land use change impacts the connectivity, complexity, and stability of microbial C-cycling gene networks across an agricultural mosaic landscape in Canterbury, New Zealand. The most densely connected networks were found in land uses that were under the most intensive agricultural management, or under naturally regenerating vegetation. The microbial C-cycling gene networks from both land uses presented high network connectivity, low modularity, and a low proportion of negative gene interactions. In contrast, microbial C-cycling genes from native forests, which had the most stable and undisturbed plant cover, had the lowest network connectivity, highest modularity, and a greater proportion of negative gene interactions. Although the differences in total soil C content between land uses were small, the large effects of land use on the network structure of microbial C-cycling genes may have important implications for long-term microbial soil C cycling. Furthermore, this research highlights the value of using microbial network analysis to study the metabolic gene interactions shaping the functional structure of soil microbial communities in a manner not typically captured by more traditional forms of microbial diversity analysis.

Karst caves, formed from the dissolution of soluble rocks, are characterized by the absence of photosynthetic activity and low levels of organic matter. Organisms evolve under these particular conditions, which causes high levels of endemic biodiversity in both macroorganism and microbes. Recent research has highlighted the presence of testate amoebae (Arcellinida) group in cave environments. This study investigates the diversity of Arcellinida in Dinaric karstic caves in Croatia, a global diversity hotspot, focusing on the influence of bat guano on community structure. Sediment samples were collected from two independent hydrosystems, and a metabarcoding approach was used to assess Arcellinida diversity at specific and intraspecific levels, using Arcellinid-specific primers to amplify the mitochondrial cytochrome oxidase subunit I (COI) region. Results reveal a significant impact of guano on both specific and intraspecific diversity of Arcellinida. Communities in guano-rich sites displayed higher diversity, abundance, and the presence of unique OTUs and genetic variants not observed in other habitats, highlighting the crucial role of bats as ecosystem engineers. In contrast, sites without guano hosted communities with low abundance and reduced biodiversity. These differences suggest the existence of guano-associated Arcellinida communities. This study provides new insights into the biodiversity of subterranean ecosystems and the ecological roles of Arcellinida in karstic environments.

Microorganisms are preferred as an enzyme source due to their short lifespan, high production rate, affordability, and absence of harmful chemicals in enzymes generated from plant and animal sources. Fungi communities are biological factories for many bioactive compounds such as the important industrial enzyme pectinase. The current study dealt with production, optimization, purification, biocompatibility, and application of fungal pectinase obtained from five plant rhizospheres (banana, jarawa, lemon, tomato, and wheat) at Fayoum Governorate, Egypt. The highest pectinase degrading index (PDI) was scored for FB5, FJ2, and FW1 isolates. Pectinase production was also examined quantitively and the highest output of 1603.67, 1311.22, and 1264.83 U/ml was gained by FB5, FJ1, and FW1 fungal isolates, respectively. The most active pectinase-producing fungi were identified as Aspergillus niveus strain AUMC1624, A. niger strain AUMC16245, and A. brasiliensis strain AUMC16244, respectively. For pectinase production optimization, one factor at a time (OFAT) protocol was applied and revealed that A. niger, A. niveus, and A. brasiliensis reached maximum pectinase levels at 1% pectin after 5, 7, and 7 days, at 40, 45, and 45 °C, respectively. Obtained pectinases were partially purified using ammonium sulfate precipitation (ASP) and organic solvent precipitation (OSP) methods. The highest activity using the ASP method scored at 40-60% saturation with A. niger. The thermostability characterization of A. niger pectinase was reached with relative activities of 61.7, 69.0, 99.9, 91.3, and 90.6% at temperatures ranging between 30 and 70 °C. pH optimized at pH 5-7. The enzyme's molecular weight was approximately 30 kDa. The GC-mass analysis of pectinase end products included acetic acid ethyl ester, hexadecane carbonsaure methylase, and hexadecenoic acid. The biocompatibility was examined using a human skin cell line (HFb-4) for the first time, with a minimal half concentration (IC₅₀) of 151.86 ± 0.76 U/ml. The biocompatible pectinase was applied as a clothes bioscouring agent with different concentrations of 1893.52 U/ml achieving the highest bioscouring with 20.0%.