Boreal peat properties link to plant functional traits of ecosystem engineers

Aims

Warming has the potential to alter plant litter mass loss and nutrient release during decomposition. However, a great deal of uncertainty remains concerning how other factors such as litter species or substrate quality might modify the effects of increased temperature on decomposition. Meanwhile, the temperature sensitivity of plant litter decay in tropical and subtropical forest ecosystems remains poorly resolved.

Methods

This study was designed to assess the effects of experimental warming on litter decomposition and nutrient release of two contrasting tree species (Schima superba and Machilus breviflora) by translocating model forest ecosystems from the high-elevation sites to the lower-elevation sites in subtropical China. Translocating model mountain evergreen broad-leaved forest (MEBF) to the altitude of 300 m and 30 m increased the average monthly soil temperature at 5 cm depth by 0.88 and 1.84 °C, respectively during the experimental period. Translocating model coniferous and broad-leaved mixed forest (CBMF) to the altitude of 30 m increased the average monthly soil temperature at 5 cm depth by 0.85 °C.

Results

We found that experimental warming accelerated litter decomposition in both model forest types, and the promoting efficiency was greater when the temperature increased. The litter with high quality (Schima superba) had stronger response to warming than low quality litter (Machilus breviflora). Warming accelerated Na, K, Mg, P, N and Ca release from Schima superba litter, but only simulated Ca release from Machilus breviflora litter. Overall, litter decomposition was controlled by the order: soil temperature > litter quality > soil moisture > litter incubation forest type under experimental warming in the subtropical China.

Conclusion

We conclude that leaf litter decomposition was facilitated by experimental warming in subtropical China. Litter species might modify the effects of increased temperature on litter decomposition; however, forest type has no effect on litter decomposition.

     

Non-native liana, <Emphasis Type="Italic">Euonymus fortunei</Emphasis>, associated with increased soil nutrients,unique bacterial communities,and faster decomposition rate

Invasive plants have wide-ranging impacts on native systems including reducing native plant richness and altering soil chemistry, microbes, and nutrient cycling. Increasingly, these effects are found to linger long after removal of the invader. We examined how soil chemistry, bacterial communities, and litter decomposition varied with cover of Euonymus fortunei, an invasive evergreen liana, in two central Kentucky deciduous forests. In one forest, E. fortunei invaded in the late 1990s but invasion remained patchy and we paired invaded and uninvaded plots to examine the associations between E. fortunei cover and our response variables. In the second forest, E. fortunei had completely invaded the forest by 2005; areas where it had been selectively removed by 2010 were paired with an adjacent invaded plot. Where E. fortunei had patchily invaded, E. fortunei patches had up to 3.5× nitrogen, 2.7× carbon, and 1.9× more labile glomalin in soils than uninvaded plots, whereas there were no differences in soil characteristics between invaded and removal plots. In the patchily invaded forest, bacterial community composition varied among invaded and non-invaded plots, whereas bacterial communities did not vary among invaded and removal plots. Finally, E. fortunei leaf litter decomposed faster (k = 4.91 year^?1) than the native liana (k = 3.77 year^?1), Vitis vulpina; decomposition of both E. fortunei and V. vulpina was faster in invaded (k = 7.10 year^?1) than removal plots (k = 4.77 year^?1). Our findings suggest that E. fortunei invasion increases the rate of leaf litter decomposition via high-quality litter, alters the decomposition environment, and shifts in the soil biotic communities associated with a dense mat of wintercreeper. Land managers with limited resources should target the densest mats for the greatest restoration potential and remove wintercreeper patches before they establish dense mats.     

Leaf Litter Consumption by Macroarthropods and Burial of their Faeces Enhance Decomposition in a Mediterranean Ecosystem

In many terrestrial ecosystems, large amounts of leaf litter are consumed by macroarthropods. Most of it is deposited as faeces that are easily transferred into deeper soil layers. However, the decomposition of this large pool of organic matter remains poorly studied. We addressed the question of how leaf litter transformation into macroarthropod faeces, and their burial in the soil, affect organic matter decomposition in a Mediterranean dry shrubland. We compared mass loss of intact leaf litter of two dominant shrub species (Quercus coccifera, Cistus albidus) with that of leaf litter-specific faeces from the abundant millipede Ommatoiulus sabulosus. Leaf litter and faeces were exposed in the field for 1 year, either on the soil surface or buried at 5 cm soil depth. Chemical and physical quality of faeces differed strongly from that of leaf litter, but distinctively between the two shrub species. On the soil surface, faeces decomposed faster than intact leaf litter in Quercus, but at similar rates in Cistus. When buried in the soil, faeces and leaf litter decomposed at similar rates in either species, but significantly faster compared to the soil surface, most likely because of higher moisture within the soil enhancing microbial activity. The combined effects of leaf litter transformation into faeces and their subsequent burial in the topsoil led to a 1.5-fold increase in the annual mass loss. These direct and indirect macroarthropod effects on ecosystem-scale decomposition are likely more widespread than currently acknowledged, and may play a particularly important role in drought-influenced ecosystems.     

Tracking an invasion: community changes in hardwood forests following the arrival of <Emphasis Type="Italic">Amynthas agrestis</Emphasis> and <Emphasis Type="Italic">Amynthas tokioensis</Emphasis> in Wisconsin

Because Upper Midwest temperate forests lack native earthworms, the invasions of European and Asian earthworms can significantly alter soils and understory vegetation. Earthworms’ ability to increase leaf litter decay, alter nutrient cycling by mixing the organic layer with mineral soil, and decrease plant species richness leads to concern about the Asian ‘jumping earthworm’ (Amynthas agrestis and A. tokioensis) species that were recorded in the University of Wisconsin—Madison Arboretum in 2013. In 2015, we found A. agrestis and A. tokioensis in a distinct 8-ha region of a 23-ha hardwood forest surveyed in the Arboretum; by 2016 A. agrestis and A. tokioensis had spread over an additional 7 ha. Plots also contained the European earthworm species Lumbricus terrestris, L. rubellus, and Apporectodea spp., whose distributions decreased from 2015 to 2016. While leaf litter, plant species richness, and tree and shrub seedling abundance were generally reduced in areas with European earthworms, they were typically slightly increased in areas with A. agrestis and A. tokioensis versus those without. Although our results do not show substantial impacts of A. agrestis and A. tokioensis on vegetation in the initial years of invasion, the rapid replacement of European earthworms by A. agrestis and A. tokioensis suggests continued monitoring of these new invasive species is important to better understand their potential to change the Upper Midwest’s forests.     

<Emphasis Type="Italic">Fusarium equiseti</Emphasis> LPSC 1166 and its in vitro role in the decay of <Emphasis Type="Italic">Heterostachys ritteriana</Emphasis> leaf litter

The role of microorganisms in litter degradation in arid and semi-arid zones, where soil and water salinization is one of the main factors limiting carbon turnover and decay, remains obscure. Heterostachys ritteriana (Amaranthaceae), a halophyte shrub growing in arid environments such as “Salinas Grandes” (Córdoba, Argentina), appears to be the main source of organic matter in the area. Little is known regarding the microorganisms associated with H. ritteriana, although they are a potential source of enzymes such as cellulolytic ones, which might be important in biotechnological fields such as bioethanol production using ionic liquids. In the present study, by studying the microbiota growing on H. ritteriana leaf litter in “Salinas Grandes,” we isolated the cellulolytic fungus Fusarium equiseti LPSC 1166, which grew and degraded leaf litter under salt stress. The growth of this fungus was a function of the C substrate and the presence of NaCl. Although in vitro the fungus used both soluble and polymeric compounds from H. ritteriana litter and synthesized extracellular β-1,4 endoglucanases, its activity was reduced by 10% NaCl. Based on these results, F. equiseti LPSC 1166 can be described as a halotolerant cellulolytic fungus most probably playing a key role in the decay of H. ritteriana leaf litter in “Salinas Grandes.”     

Alteration of soil properties by the invasive tree <Emphasis Type="Italic">Psidium cattleianum</Emphasis> along a precipitation gradient on O'ahu Island,Hawai'i

To test the effects of invasion by strawberry guava trees (Psidium cattleianum) on the forest soil ecosystem, we compared soil properties between pairs of adjacent native and P. cattleianum stands. We set up six study sites that had developed under different mean annual precipitation levels in the Ko'olau Mountains on the island of O'ahu, Hawai'i. Accumulated litter mass and soil pH decreased with precipitation in the native stands. Invasion by P. cattleianum increased the amount of litter and reduced the differences in soil water content and pH among the sites. We compared the decomposition process using the Tea Bag Index, which is determined by the difference in dry mass of commercially available green and rooibos teas in nylon mesh bags before and after 90 days of burial. Psidium cattleianum increased the initial litter decomposition rate irrespective of precipitation and other soil properties. On the other hand, P. cattleianum increased the long-term litter stabilization factor of the Tea Bag Index in wetter sites. The accumulation of litter was likely caused by indirect effects of P. cattleianum through the alteration of soil moisture properties. In summary, this study shows that invasion by P. cattleianum could alter the soil properties in both wet and mesic sites, suggesting the possibility of change in composition and/or function of decomposers.     

<Emphasis Type="Italic">Artemisia arborescens</Emphasis> L. leaf litter: phytotoxic activity and phytochemical characterization

Artemisia arborescens L. is a perennial fast-growing Mediterranean shrub, which releases abundant leaf litter upon soil surface throughout the year. The paper aimed to both evaluate the phytotoxic potential and identify major compounds occurring in the plant leaf litter. Following methanolic maceration of the leaf litter, the crude extract was then sequentially extracted with hexane, chloroform and ethyl acetate through a bio-guided fractionation method. The phytotoxic potential of the methanolic extract and its solvent fractions was assessed in vitro on germination and root growth of two sensitive (Lactuca sativa L., Raphanus sativus L.) and native (Amaranthus retroflexus L., Cynodon dactylon (L.) Pers.) species. Moreover, the most active fractions were chemically characterized by GC–MS and HPTLC analysis. In all species, the physiological processes were highly inhibited by both the methanolic extract and its solvent fractions. Several classes of biologically active phytochemicals such as terpenoids, fatty acids, lignans and phenolic compounds were identified in all fractions. Artemisia arborescens leaf litter could be considered an important source of biologically active phytochemicals, which may have a significant allelopathic impact towards neighbouring species once released into the environment.     

Yeast communities of <Emphasis Type="Italic">Formica aquilonia</Emphasis> colonies

Yeast abundance and species diversity in the colonies of Formica aquilonia ants in birch–pine grass forest near Novosibirsk, Russia, were studied. The average yeast number in the anthill material was 10³–10⁴ CFU/g, reaching 10⁵ CFU/g in the hatching chambers. Typical litter species (Trichosporon moniliiforme and Cystofilobasidium capitatum) were predominant in soil and litter around the anthills. Apart from these species, ascomycete species of the family Debaryomycetaceae, Debaryomyces hansenii, and Schwanniomyces vanrijiae were predominant in the anthill material. Yeast population of the ant’ bodies consisted exclusively of the members of the last two species. Thus, highly specific yeast communities formed in the colonies of Formica aquilonia ants differ from the communities of surrounding soil. These differences are caused by environment-forming activity of the ants.     

Testate amoebae (Testacea) in a <Emphasis Type="Italic">Formica lugubris</Emphasis> nest: Fauna composition and structure

The fauna of testate amoebae (Testacea) in a Formica lugubris anthill and in litter layers from the control soil area in a spruce forest, Moscow region, was represented by a total of 43 species and subspecies. Their numbers ranged from 11000 ind./g air-dry substrate in the surface layer of the anthill to 62000 ind./g in the lower litter layer A0H/A1, with variation in species diversity between the samples being insignificant (24–30 species). Representatives of the genera Centropyxis, Cyclopyxis, Plagiopyxis, Corythion, and Trinema were dominant, whereas most of other species were few in numbers. The group of testacean species in the anthill was not specific, being a derivative of the testacean complex inhabiting the surrounding soil. Differences between litter layers and between these layers and substrates from the anthill concerned mainly the composition of the testacean community, which proved to change in the course of plant material decomposition: the aerophilic complex of upper layers (dominated by Centropyxis aerophila and Trinema lineare) was substituted by an edaphophilic complex (with Plagiopyxis declivis being dominant) in the nest mound of the anthill and in the lower litter layers. Plagiopyxis penardi was a eudominant species in the nest mound. Its especially high abundance is explained by deep transformation of plant remains in the nest (from moder to mull-like substrate) as the result of ant life activities.     

The Effects of Differences in Vegetation on Calcium Dynamics in Headwater Streams

Although organisms can alter dynamics of elements in ecosystems via physiological results, the effects of tree species on ecosystem nutrient dynamics are highly uncertain. A four-fold variation in the calcium concentrations of streams, soils and leaf litters were caused by the planting of Cryptomeria japonica in south-central Japan. In this study, we examined how the calcium dynamics were affected by the planting of C. japonica through strontium isotope analysis. We predicted the planting of C. japonica would result in the calcium concentration increasing because of the significant dissolution of calcium from bedrock. In a forest ecosystem, calcium is usually derived from precipitation and bedrock weathering, and their relative contributions can be estimated using a strontium isotope mixing model. Therefore, we collected stream water, litter, soil, precipitation and bedrock samples from 17 sites in catchments dominated by C. japonica plantation or evergreen broad-leaved forest; after collection, we analyzed the sample chemical compositions and strontium isotope ratios. The calcium concentrations in the stream water and the water-soluble calcium in the soil were significantly higher at sites dominated by C. japonica than at broad-leaved forest sites. Strontium isotope analysis indicated that there was more calcium from the bedrock present in stream water at sites dominated by C. japonica than in stream water at broad-leaved forest sites. Our results showed that watershed-scale dynamics of calcium and other cations can be altered by the type of vegetation in a catchment due to the effects of vegetation on the supply of calcium from bedrock.     

Influence of <Emphasis Type="Italic">Lumbricus terrestris</Emphasis> earthworms on the structure of the yeast community of forest litter

The taxonomic structure of yeast communities was studied in forest litter and soil, as well as in substrates transformed by the activity of Lumbricus terrestris earthworms (leaves in heaps, the gut contents, and coproliths). The activity of L. terrestris has a weak effect on the total yeast abundance but results in substantial changes in the community taxonomic composition. The share of ascomycetous yeasts is significantly higher in the substrates associated with the activity of earthworms. The teleomorphic ascomycetes Williopsis saturnus were isolated from the gut contents. The effect of earthworms on the composition of the yeast community in the process of forest litter destruction is more pronounced than seasonal changes.     

Hydrogen sulfide mediates ion fluxes inducing stomatal closure in response to drought stress in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Background and aims

Changes in net primary productivity in response to climate change are likely to affect litter inputs to forest soil. However, feedbacks between changes in litter input and soil carbon dynamics remain poorly understood in tropical and subtropical forests. This study aims to test whether the effects of litter manipulation on soil respiration differ between natural and plantation forests.

Methods

Soil respiration, soil properties, fine root biomass and enzyme activity were measured in adjacent plots with doubling vs. eliminating litter input in both natural and plantation forests of Castanopsis carlesii in southern China.

Results

After only 3 years of litter manipulation, the magnitude of change in soil respiration was greater in response to a doubling of the litter input (+24%) than to the elimination of litter input (?15%) in the natural forest, possibly due to a positive priming effect on decomposition of soil organic carbon (SOC). The quick and intense priming effect was corroborated by elevated enzyme activities for five of the six enzymes analyzed. In contrast, the response to litter removal (?31%) was greater than the response to litter addition (1%; not significant) in the plantation forest. The lack of positive priming in the plantation forest may be related to its lower soil fertility, which could not meet the demand of soil microbes, and to its high clay content, which protected SOC from microbial attack. The positive priming effect in the natural forest but not plantation forest of C. carlesii is also consistent with the significant declines in total soil carbon observed following litter addition in the natural forest but not the plantation forest.

Conclusions

Increases in aboveground litter production may trigger priming effects and subsequently transfer more soil carbon to atmospheric CO₂ in the natural forest but not in the plantation forest with low fertility. Changes in litter inputs resulting from global change drivers may have different impacts on natural and plantation forests.

     

Does tree species composition affect soil CO<Subscript>2</Subscript> emission and soil organic carbon storage in plantations?

Key message

Mixed tree plantations are potential silvicultural systems to increase soil carbon storage through altering litter and root inputs and soil physiochemical properties.

Abstract

Afforestation and reforestation are major strategies for global climate change mitigation. Different tree species composition can induce diverse changes in soil CO₂ emission and soil carbon sequestration in tree plantation. This study employed three plantations of monoculture and mixed Pinus yunnanensis and Eucalyptus globulus to estimate the effect of tree species composition on soil CO₂ emission and soil organic carbon storage in subtropical China. We found that tree species composition had a significant effect on the soil CO₂ emission and soil organic carbon storage. Soil CO₂ emission was lower in the mixed plantation than in the P. yunnanensis plantation, whereas it was higher than in the E. globulus plantation. Differences in soil CO₂ emission among the three plantations were determined by leaf litterfall mass, fine root biomass, soil available nitrogen, pH, soil bulk density, and soil C:N ratio. Soil organic carbon storage was 34.5 and 23.2 % higher in the mixed plantation than in the P. yunnanensis and E. globulus plantations, respectively. Higher soil organic carbon stock in the mixed plantation was attributed to lower C/N ratio of leaf litter and soil, greater fine root biomass and soil organic carbon content, and lower soil CO₂ emission. We conclude that mixed tree plantation can enhance soil carbon sequestration, but can decrease or increase soil CO₂ emission through altering litter and root inputs and soil physiochemical properties.

     

Effects of leaf litter on inter-specific competitive ability of the invasive plant <Emphasis Type="Italic">Wedelia trilobata</Emphasis>

Allelochemicals released by invasive plants contribute to the successful invasion of new habitats. However, the relationship between allelopathic effects and competitive ability of invasive plants has not been characterized. We quantified the neighbor effects of Wedelia trilobata (family: Asteraceae) and the allelopathic effects of its leaf litter on two Asteraceae competitor species (invasive Eupatorium catarium and non-invasive Lactuca sativa) and on its own ramet growth. The seed germination rate and seedling biomass of the two competitor species decreased following treatment with W. trilobata leaf extracts. When co-cultured with W. trilobata, the total biomass of the two competitor species significantly decreased regardless of whether leaf extracts were present. Under low plant density co-culture conditions, W. trilobata leaf extracts enhanced the inhibitory effects on E. catarium. In contrast, W. trilobata leaf extracts promoted the growth of W. trilobata adventitious roots, resulting in increased competitive ability. Therefore, W. trilobata growth was promoted by its own allelochemicals in leaf extracts, whereas the growth of the invasive and non-invasive competitors was inhibited by the same chemicals. These responses facilitated the invasion by W. trilobata. Our study demonstrates that leaf litter of invasive plants may inhibit the growth of neighboring species to enhance the competitive ability of the invasive plants during the early stages of invasion.     

Soil microbial communities buffer physiological responses to drought stress in three hardwood species

Trees possess myriad adaptations for coping with drought stress, but the extent to which their drought responses are influenced by interactions with soil microbes is poorly understood. To explore the role of microbes in mediating tree responses to drought stress, we exposed saplings of three species (Acer saccharum, Liriodendron tulipifera, and Quercus alba) to a four week experimental drought in mesocosms. Half of the pots were inoculated with a live soil slurry (i.e., a microbial inoculum derived from soils beneath the canopies of mature A. saccharum, L. tulipifera or Q. alba stands), while the other half of the pots received a sterile soil slurry. Soil microbes ameliorated drought stress in L. tulipifera by minimizing reductions in leaf water potential and by reducing photosynthetic declines. In A. saccharum, soil microbes reduced drought stress by lessening declines in leaf water potential, though these changes did not buffer the trees from declining photosynthetic rates. In Q. alba, soil microbes had no effects on leaf physiological parameters during drought stress. In all species, microbes had no significant effects on dynamic C allocation during drought stress, suggesting that microbial effects on plant physiology were unrelated to source–sink dynamics. Collectively, our results suggest that soil microbes have the potential to alter key parameters that are used to diagnose drought sensitivity (i.e., isohydry or anisohydry). To the extent that our results reflect dynamics occurring in forests, a revised perspective on plant hydraulic strategies that considers root-microbe interactions may lead to improved predictions of forest vulnerability to drought.     

The effects of vegetation types and microhabitats on carabid beetle community composition in cool temperate Japan

The effects of vegetation types and environmental factors on carabid beetle (Coleoptera: Carabidae) communities were studied. Carabid beetles were collected using pitfall traps (total 2844 trapping days) and seven microenvironmental factors were measured in four vegetation types: grassland, natural evergreen coniferous forest (Pinus densiflora), deciduous broad-leaved natural forest (Quercus crispula, Betula platyphylla, Alnus japonica, or Fagus crenata), and deciduous coniferous plantation (Larix kaempferi) in cool temperate Japan. These four vegetation types provided a novel comparison between natural forests and plantations because the vast majority of related studies have investigated only deciduous broad-leaved natural forests and evergreen coniferous plantations. PERMANOVA indicated that vegetation types affected carabid community composition. Ordination plots showed that community composition differed greatly between grassland and forest vegetation types, but that community composition in the plantation forest overlapped with that of natural forest types. Characteristics differentiating the grassland included a high proportion of winged species and a low mean carabid body weight. Among the examined environmental factors, litter depth, soil water content, and depth of the soil A-horizon had large effects on carabid communities. These results suggest that the effect of afforestation on carabid communities in cool temperate Japan might be insignificant compared with the effects of cover types (deciduous vs. evergreen) and microenvironmental factors.     

Drivers of invasive tree and shrub natural regeneration in temperate forests

We assessed drivers of ecological success along resource availability gradients for three invasive woody species: Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L. We aimed to check how much of invasion success, measured by invader biomass, is explained by propagule pressure and plant community invasibility. Using 3 years of observations from 372 study plots (100 m² each) in temperate forests of Wielkopolski National Park (Poland) we investigated the hierarchy of predictors and partial dependencies using the random forest method. Our study indicated that propagule pressure explained more variance in success of invaders than invasibility—describing availability of resources and competitors in understory vegetation. We also found different responses of seedlings and saplings, connected with dependence on stored carbohydrates, which decreased seedling responses to resource availability gradients. However, resource availability (light and leaf litter predictors) had greater influence than predictors describing understory vegetation. Based on importance and response strength the species studied may be arranged by decreasing requirements for soil fertility and acidity: P. serotina?<?Q. rubra?<?R. pseudoacacia, whereas for light requirements and competition vulnerability the order is: P. serotina?>?Q. rubra?>?R. pseudoacacia. However, low light requirements of R. pseudoacacia may be biased by high proportion of sprouts supplied by parental trees. Results provide guidelines for effective management of invasive woody species in forest ecosystems and describe complex interactions between factors studied on ecological success of invaders.     

Four novel <Emphasis Type="Italic">Talaromyces</Emphasis> species isolated from leaf litter from Colombian Amazon rain forests

Various Talaromyces strains were isolated during a survey of fungi involved in leaf litter decomposition in tropical lowland forests in the Caquetá and Amacayacu areas of the Colombian Amazon. Four new Talaromyces species are described using a polyphasic approach, which includes phenotypic characters, extrolite profiles and phylogenetic analysis of the internal transcribed spacer region (ITS) barcode, and beta-tubulin (BenA) and calmodulin (CaM) gene regions. Talaromyces amazonensis sp. nov., T. francoae sp. nov. and T. purgamentorum sp. nov. belong to Talaromyces section Talaromyces, and T. columbiensis sp. nov. is located in section Bacillispori. The new species produce several bioactive compounds: T. amazonensis produces the potential anticancer agents duclauxin, berkelic acid and vermicillin, and T. columbiensis produces the effective anticancer agent wortmannin (together with duclauxin). In addition to the new species, T. aculeatus and T. macrosporus were isolated during this study on leaf litter decomposition.     

Bacterial DNA detected on pathologically changed heart valves using 16S rRNA gene amplification

Nowadays, dental diseases are one of the most common illnesses in the world. Some of them can lead to translocation of oral bacteria to the bloodstream causing intermittent bacteraemia. Therefore, a potential association between oral infection and cardiovascular diseases has been discussed in recent years as a result of adhesion of oral microbes to the heart valves. The aim of this study was to detect oral bacteria on pathologically changed heart valves not caused by infective endocarditis. In the study, patients with pathologically changed heart valves were involved. Samples of heart valves removed during heart valve replacement surgery were cut into two parts. One aliquot was cultivated aerobically and anaerobically. Bacterial DNA was extracted using Ultra-Deep Microbiome Prep (Molzym GmbH, Bremen, Germany) followed by a 16S rRNA gene PCR amplification using Mastermix 16S Complete kit (Molzym GmbH, Bremen, Germany). Positive PCR products were sequenced and the sequences were analyzed using BLAST database (http://www.ncbi.nlm.nih/BLAST). During the study period, 41 samples were processed. Bacterial DNA of the following bacteria was detected in 21 samples: Cutibacterium acnes (formerly Propionibacterium acnes) (n?=?11; 52.38% of patients with positive bacterial DNA detection), Staphylococcus sp. (n?=?9; 42.86%), Streptococcus sp. (n?=?1; 4.76%), Streptococcus sanguinis (n?=?4; 19.05%), Streptococcus oralis (n?=?1; 4.76%), Carnobacterium sp. (n?=?1; 4.76%), Bacillus sp. (n?=?2; 9.52%), and Bergeyella sp. (n?=?1; 4.76%). In nine samples, multiple bacteria were found. Our results showed significant appearance of bacteria on pathologically changed heart valves in patients with no symptoms of infective endocarditis.