Information about the fungal composition of bee bread, and the fermentation processes to which the fungi contribute significantly, is rather scarce or fragmentary. In this study, we performed an NGS-based metagenomics snapshot picture study of the fungal composition of bee bread in four locations in Bulgaria during the most active honeybee foraging period at the end of June 2020. The sampling locations were chosen to differ significantly in climatic conditions, landscape, and anthropogenic pressure, and the Illumina 2 × 250 paired-end reads platform was used for amplicon metagenomics study of the ITS2 region. We found that some of the already reported canonical beneficial core fungal species were present within the studied samples. However, some fungal genera such as Monilinia, Sclerotinia, Golovinomyces, Toxicocladosporium, Pseudopithomyces, Podosphaera and Septoriella were reported for the first time among the dominant genera for a honeybee related product. Anthropogenic pressure negatively influences the fungal composition of the bee bread in two different ways—urban/industrial pressure affects the presence of pathogenic species, while agricultural pressure is reflected in a decrease of the ratio of the beneficial fungi.

An amplicon-based metagenomic survey of archaea, fungi, and bacteria was performed on Livingston Island, Maritime Antarctica. In many of the samples, patterns of antagonism between these three superkingdoms were observed in the form of an inversely proportional dependence of the richnesses of the three types of microorganisms. The antagonism was quantified—based on the observed numbers of the total tags and the numbers of the operational taxonomic units (OTUs), and on four alpha diversity parameters—using the Shannon, the Simpson, the Chao1, and the ACE indices. We found that the most discriminative results in the antagonism measuring were obtained when the numbers of the OTUs and the ACE community richness estimator were compared. The antagonism between archaea and fungi was most potent, followed by that of archaea and bacteria. The fungi–bacteria antagonism was slightly detectable. Pearson and Spearman correlation analyses also showed a statistically significant negative correlation between the fungal and archaeal effective tags, while the correlation between archaeal and bacterial diversity was positive. Indications of the order of primary microbial succession in barren ecological niches were also observed, demonstrating that archaea and bacteria are the pioneers, followed by fungi, which would displace archaea over time.

As a flexible and environmentally friendly technology, bioleaching is widely used to recover base metals from raw materials and industrial waste. This study aimed to test and compare the bioleaching potential of the fungi Aspergillus niger and Penicillium ochrochloron for copper, zinc, and cobalt...

The main scientific interest for decades remained focused primarily on physical and chemical air pollutants, which severely limited our knowledge of microbial diversity in the atmosphere. The ecology of airborne microorganisms is poorly understood, even though they are a constant element of the air we breathe. Their exploration is very important for understanding health and ecological impacts, mainly in the highly urbanized cities. The main purpose of this study is to explore the biodiversity of microorganisms in the atmosphere over the densely populated centre of Sofia (Bulgaria) during spring and winter by Next-generation sequencing. The results showed that the most prevailing bacteria in the urban bioaerosols were representatives of phyla Firmicutes, Proteobacteria, Bacteroides, Actinobacteria. Many of the identified species were soil and leaf surface dwellers. Most of the detected fungal sequences belong to the phylum Ascomycota. Some pathogenic bacterial and fungal taxa were also found. This study provides the first information about microbial diversity in the outdoor air above Sofia and contributes to better understanding of urban airborne microbiota.

Copper slag, a by-product of copper ore and concentrate smelting, is rich in non-ferrous metals; therefore, it has been considered a valuable raw material in recent years. This study aimed to compare the extraction of zinc, copper, and cobalt from two types of copper slag from a dump located near the village of Eliseyna, Bulgaria, which differ in mineralogical composition and chemical content, using indirect bioleaching with a spent medium of Aspergillus niger and Penicillium ochrochloron. Chemical leaching with sulphuric acid revealed that zinc and cobalt existed mainly as an acidic-soluble phase in both types of copper slag. In contrast, it contained 50–75% of the total copper content. Each fungal species was cultivated for one week, and the biomass and the spent medium were separated a week later. Owing to the production of a higher concentration of citric acid, A. niger facilitated more efficient base metal recovery. However, their effective recovery from the acidic-soluble phase required leaching at a 5% pulp density and supplementing the spent medium with sulphuric acid. The temperature played a secondary role. Conclusions: Non-ferrous metal extraction from copper slag exposed to weathering using a spent medium supplemented with sulphuric acid was achieved under milder leaching conditions and with better selectivity. In contrast, slag unaffected by weathering behaved as a refractory due to the worsened results of base metal extraction under similar experimental conditions.

In terms of air quality, Sofia, Bulgaria, is one of Europe's most polluted capitals. The city represents a unique pollution challenge due to the combination of specific environmental and orographic features. Until now, no studies have been conducted to monitor outdoor bioaerosol concentrations. This pioneering research presents a systematic study of the seasonal cycle of bacterial and fungal aerosol concentrations in Sofia. Although the overall study extends over a full year, this paper focuses specifically on results from the spring and summer seasons. Airborne microbial samples were collected from the 1st of March 2024 to the 31st of August 2024 at an open-air location situated in a central urban area. The findings reveal a clear seasonal distribution pattern for bacterial and fungal aerosols. The mean bioaerosol concentrations during the spring-summer period were ranked in descending order as follows: a) bacterial aerosols: summer (258.0 CFU/m3) > spring (197.0 CFU/m3); (b) fungal aerosols: summer (987.0 CFU/m3) > spring (228.0 CFU/m3). This data on bioaerosol levels can be used to support future aeromicrobiology studies, policymaking, and urban planning in Sofia.