Polyphasic analysis in the description of Sulfitobacter salinus sp. nov., a marine alphaproteobacterium isolated from seawater

Microplastics, microfibers and associated microbiota biofilm analysis in seawater, a case study from the Vesuvian Coast, southern Italy

The growing concerns regarding pollution from microplastics (MPs) and microfibers (MFs) have driven the scientific community to develop new solutions for monitoring ecosystems. However, many of the proposed technologies still include protocols for treating environmental samples that may alter plastic materials, leading to inaccurate results both in observation and in counting. For this reason, we are refining a protocol, based on optical microscopy without the use of pretreatments, applicable to different environmental matrices, which allows not only counting but also a complete morphological characterization of MPs and MFs. Previously, the protocol has successfully been tested on marine sediments from the Vesuvian area of the Gulf of Naples (Italy) with good results. In the present study, we tested the protocol on MPs and MFs in seawater samples collected from the same geographical area to provide a comprehensive overview of their distribution in the marine environments. The protocol enabled not only the morphological characterization of MPs and MFs but also the collection of information on the colonies of microorganisms present on the microparticles. Next Generation Sequencing (NGS) metagenomic technologies enabled us to characterize the microbiota composition of the sampled MPs, the so-called Plastisphere. The analytical approach allowed the characterization of several potentially pathogenic bacteria, which represent a potential threat to the environment and human health. In fact, they may exploit their ability to form biofilms on plastics to proliferate in marine ecosystems.

Beyond Archaea: The Table Salt Bacteriome

Commercial table salt is a condiment with food preservative properties by decreasing water activity and increasing osmotic pressure. Salt is also a source of halophilic bacteria and archaea. In the present research, the diversity of halotolerant and halophilic microorganisms was studied in six commercial table salts by culture-dependent and culture-independent techniques. Three table salts were obtained from marine origins: Atlantic Ocean, Mediterranean (Ibiza Island), and Odiel marshes (supermarket marine salt). Other salts supplemented with mineral and nutritional ingredients were also used: Himalayan pink, Hawaiian black, and one with dried vegetables known as Viking salt. The results of 16S rRNA gene sequencing reveal that the salts from marine origins display a similar archaeal taxonomy, but with significant variations among genera. Archaeal taxa Halorubrum, Halobacterium, Hallobellus, Natronomonas, Haloplanus, Halonotius, Halomarina, and Haloarcula were prevalent in those three marine salts. Furthermore, the most abundant archaeal genera present in all salts were Natronomonas, Halolamina, Halonotius, Halapricum, Halobacterium, Haloarcula, and uncultured Halobacterales. Sulfitobacter sp. was the most frequent bacteria, represented almost in all salts. Other genera such as Bacillus, Enterococcus, and Flavobacterium were the most frequent taxa in the Viking, Himalayan pink, and black salts, respectively. Interestingly, the genus Salinibacter was detected only in marine-originated salts. A collection of 76 halotolerant and halophilic bacterial and haloarchaeal species was set by culturing on different media with a broad range of salinity and nutrient composition. Comparing the results of 16S rRNA gene metataxonomic and culturomics revealed that culturable bacteria Acinetobacter, Aquibacillus, Bacillus, Brevundimonas, Fictibacillus, Gracilibacillus, Halobacillus, Micrococcus, Oceanobacillus, Salibacterium, Salinibacter, Terribacillus, Thalassobacillus, and also Archaea Haloarcula, Halobacterium, and Halorubrum were identified at least in one sample by both methods. Our results show that salts from marine origins are dominated by Archaea, whereas salts from other sources or salt supplemented with ingredients are dominated by bacteria.