Cyanobactins are a large family of ribosomally synthesized and post-translationally modified cyanopeptides (RiPPs). Thus far, over a hundred cyanobactins have been detected in different free-living and symbiotic cyanobacteria. The majority of these peptides have a cyclic structure. The occurrence of linear cyanobactins, aeruginosamides and virenamide, has been reported sporadically and in few cyanobacterial taxa. In the current work, the production of cyanobactins by Limnoraphis sp. CCNP1324, isolated from the brackish water Baltic Sea, has been studied for the first time. In the strain, eighteen new aeruginosamide (AEG) variants have been detected. These compounds are characterized by the presence of prenyl and thiazole groups. A common element of AEGs produced by Limnoraphis sp. CCNP1324 is the sequence of the three C-terminal residues containing proline, pyrrolidine and methyl ester of thiazolidyne-4-carboxylic acid (Pro-Pyr-TzlCOOMe) or thiazolidyne-4-carboxylic acid (Pro-Pyr-TzlCOOH). The aeruginosamides with methylhomotyrosine (MeHTyr¹) and with the unidentified N-terminal amino acids showed strong cytotoxic activity against human breast cancer cells (T47D).

Even cyanobacteria from ecosystems of low biodiversity, such as the Baltic Sea, can constitute a rich source of bioactive metabolites. Potent toxins, enzyme inhibitors, and anticancer and antifungal agents were detected in both bloom-forming species and less commonly occurring cyanobacteria. In previous work on the Baltic Pseudanabaena galeata CCNP1313, the induction of apoptosis in the breast cancer cell line MCF-7 was documented. Here, the activity of the strain was further explored using human dermal fibroblasts, African green monkey kidney, cancer cell lines (T47D, HCT-8, and A549^ACE2/TMPRSS2) and viruses (SARS-CoV-2, HCoV-OC43, and WNV). In the tests, extracts, chromatographic fractions, and the main components of the P. galeata CCNP1313 fractions were used. The LC-MS/MS analyses of the tested samples led to the detection of forty-five peptides. For fourteen of the new peptides, putative structures were proposed based on MS/MS spectra. Although the complex samples (i.e., extracts and chromatographic fractions) showed potent cytotoxic and antiviral activities, the effects of the isolated compounds were minor. The study confirmed the significance of P. galeata CCNP1313 as a source of metabolites with potent activity. It also illustrated the difficulties in assigning the observed biological effects to specific metabolites, especially when they are produced in minute amounts.

Lack of degradability and the landfill sites closing as well as increasing water and land pollution problems have led to concern about synthetic packaging materials. Awareness of the waste problem and its influence on the environment has awakened a new interest in the field of biodegradable polymers. They are designed to degrade upon disposal by the action of living organisms. Biodegradation is governed by various factors like polymer characteristics, type of microorganism, and the nature of pre-treatment. The polymer features such as its crystallinity, molecular weight, the type of functional groups and substituents present in its structure, and additives added to the polymer all play an important role in their degradation. In nature, the degradation of most synthetic plastics is a very slow process that involves environmental factors and often is followed by the action of microorganisms. Biodegradation of various polymers have been studied under diverse environments like in soil, in sewage sludge, in compost conditions, and in seawater. The aim of this chapter is to present the research on the biodegradation of the available biodegradable polymer packaging materials in seawater and on the trials to overwork the methods to estimate the impact of biodegradable polymers on sea life. Thus, the chapter is unique in its content.