A culture collection of Maltese microorganisms for application in biotechnology, biomedicine and industry

Over the years, very few studies have been conducted on microorganisms growing in the Maltese islands, and these have rarely resulted in the description of new gen- era, species or serovars. Two important exceptions are the studies on Brucella melitensis, by Sir Temi Zammit in 1905 (Wyatt, 2005) and a new serovar of Salmonella from Gozo (Vella & Cuschieri, 1995). Ten years ago, sampling of microorganisms growing as bio lms on di erent substrates around the Maltese islands was initiated. The microorganisms consisted mainly of chemoorganotrophic bacteria, cyanobacteria and microalgae. Today the culture collection of Maltese microorganisms contains over a hundred new microbial strains that are new to science and which include fresh- water, marine, soil and subaerophytic microorganisms. The aim of the research is twofold. Firstly, it is im- portant to characterise the Maltese microbial strains and describe new taxa as required. Secondly, the ex- traction of important metabolites for application in bi- otechnology, biomedicine and industrypeer-reviewe

Maltese microalgae and global climate variability

The biodiversity of cyanobacteria and microalgae growing in terrestrial and marine habitats around the Maltese islands is currently being investigated, as limited knowledge exists about the phototrophic microorganisms inhabiting this geographical area. New strains of the genera Oculatella, Albertania, Nodosilinea, Nostoc, Lyngbya, Oscillatoria, Calothrix and Jenufa have been recorded recently. Since the phototrophic microbial biodiversity is currently largely unknown, there is an imminent risk of undescribed microorganisms being lost as a result of changes in microbial community structures due to global climate variability (GCV). We describe a six-month experiment to assess the effects of GCV on two Maltese microorganisms, the filamentous heterocytous cyanobacterial Nostoc strain AD0303 and a coccal microalgal Jenufa strain AD0402. Each strain was cultured under environmental conditions associated with GCV; a temperature (T) of 26 C, enhanced ultraviolet radiation (UVR) and an increased CO2 concentration. Elevated T stimulated growth and biomass accumulation of Nostoc AD0303, whereas growth of Jenufa AD0402 was partially inhibited. Increased UVR had the most prominent effect on cellular morphology. Nostoc AD0303 presented as aggregated filaments, whereas Jenufa AD0402 exhibited thicker cell walls. These UV-protecting mechanisms allowed both strains to accumulate biomass at a significantly higher rate than the control. An increase in CO2 concentration resulted in inhibition of growth in Jenufa AD0402 and bleaching of filaments in Nostoc AD0303, both leading to culture death. A lower CO2 concentration and re-introduction of air subsequently allowed Jenufa AD0402 to grow. So far, this demonstrates that the effects imposed by climate variability are strain-specific, making changes at an ecosystem level difficult to predict.peer-reviewe

Phototrophic biofilms and microbial mats from the marine littoral of the central Mediterranean

Phototrophic biofilm and microbial mat communities grow along the rocky coastline of the Maltese islands. This research involved studying phototrophs from the mediolittoral and supralittoral zones over a two-year period and seasonal changes were observed. Attachment of pioneer microorganisms to the porous eroded limestone bedrock was facilitated via a gelatinous matrix composed of exopolymeric substances (EPS). In submerged areas, such as undisturbed rock pools, these progressively formed green or brown compact biofilms, some of which thickened over the spring to form microbial mats via the production of more extensive EPS layers. Microbial mats gradually attained a lighter colouration due to the presence of ultraviolet (UV) screening pigments. In full summer, they were observed to shrink, detach from the exposed substrate, harden and progressively calcify. Biofilm microorganisms survived the harsh summer months in sheltered areas. The major biofilm formers were filamentous non-heterocytous cyanobacteria belonging to the Leptolyngbyaceae, Pseudanabaenaceae and Oscillatoriaceae. Their sheaths were thick, lamellated and often confluent. A higher biodiversity of phototrophs was observed in late autumn and winter, when tufts of heterocytous Calothrix sp. grew on thin compact biofilms of Nodosilinea sp., Toxifilum sp. and Phormidesmis spp., while Lyngbya spp. trichomes were surrounded by thick brown sheaths. Germlings of green and brown macroalgal species belonging to Ulva, Cladophora and Sphacelaria were embedded in biofilms and microbial mats and gradually grew to form extensive macroalgal covers submerged in rock pools. Erythrotrichia sp. filaments colonised the mediolittoral zone and were confined to areas that were exposed to wave action and submerged intermittently. Over the summer, macroalgal coverage diminished and microalgal biofilms and microbial mats prevailed in rock pools

Germling culture and molecular analysis of evasive micro-filamentous green algae growing in the Maltese islands (central Mediterranean)

Acknowledgements This research was partially funded by the ENDEAVOUR Scholarship Scheme (Malta)- Group B – National Funds and by the Fusion R&I Research Excellence Programme through the Malta Council for Science and Technology. The study was also supported by the University of Malta, the Environment and Resources Authority (Malta), the Total Foundation (Paris) and the Marine Alliance for Science and Technology for Scotland pooling initiative (MASTS), the latter funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. Thanks are due to Akira F. Peters for germling isolation and to Eleni Kytinou for diving assistance.Peer reviewedPostprin

Laurencia mediterranea sp. nov. (Ceramiales, Rhodophyta) from the central Mediterranean Sea

Acknowledgements This research was funded by an award to GZ (grant REP-2022-001), for the Project ‘GreASE’, financed by the Malta Council for Science & Technology, for and on behalf of the Foundation for Science and Technology, through the FUSION: R&I Research Excellence Programme’. AGB was supported by the ENDEAVOUR Scholarship Scheme (Malta)- Group B – National Funds. FCK would like to acknowledge the TOTAL Foundation (Paris) and the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland), which is funded by the Scottish Funding Council (grant reference HR09011).Peer reviewe

Phototrophic communities colonising a rocky shore in Sliema, Malta

Phototrophic biofilms and biomats are found growing on coastal rocky shores around the Maltese islands. No detailed studies to determine the composition of these phototrophic communities have been carried out to date. This study aimed at increasing the knowledge of the genetic diversity of phototrophic biofilm- and biomat-forming organisms growing along the coastline of Sliema in Malta.peer-reviewe

The genetic diversity of biofilm communities colonising a central Mediterranean shoreline

Phototrophic biofilms and microbial mats colonise coastal rocky shores around the Maltese islands. Such communities are underinvestigated, both locally in Malta and regionally in the Mediterranean area. This study aims to increase the knowledge of the genetic diversity of phototrophic communities forming biofilms and microbial mats along a central Mediterranean shoreline, that are adapted to survive stressors of temperature, salinity and UV radiation.peer-reviewe

Phototrophs of the marine littoral : strategies for biofilm and biomat formation

Phototrophic biofilm and biomat communities grow along the rocky coastline of the Maltese islands. During this study, the phototrophs growing in the mediolittoral and supralittoral zones of different locations were studied over a period of a year and seasonal changes were observed. Attachment of pioneer microorganisms to the porous eroded limestone bedrock was facilitated via a gelatinous polymeric matrix. In submerged areas, such as undisturbed rock pools or salt pans, these progressively formed green or brown coloured compact biofilms.peer-reviewe

The current state of DNA barcoding of macroalgae in the Mediterranean Sea : presently lacking but urgently required

The research work disclosed in this publication is partially funded by the ENDEAVOUR Scholarship Scheme (Malta)-Group B – National Funds. FCK would also like to thank the UK Natural Environment Research Council (grants NE/D521522/1, NE/J023094/1, 2025/WP 4.5), the TOTAL Foundation (Project “Diversity of brown algae in the Eastern Mediterranean”) and the Marine Alliance for Science and Technology for Scotland (MASTS) pooling initiative, which is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. AFP was funded by the project IDEALG (France: ANR-10-BTBR-04).Peer reviewedPostprin

New records of Palisada tenerrima and Hincksia mitchelliae from the Maltese Islands revealed by molecular analysis

We report two new algal records from the Maltese islands: Hincksia mitchelliae (= Feldmannia mitchelliae) (Phaeophyceae) and Palisada tenerrima (Rhodophyceae). The former species was grown in culture from an Ulva sp. blade, while the latter was collected in the field. Our study employed an innovative integrative approach including morphological criteria as well as molecular analysis. DNA data and subsequent phylogenetic analysis of the COI gene and the rbcL plus RuBisCO spacer supported the separation of these two species from the closest-related congeners that had previously been reported from the Maltese islands.peer-reviewe