Struktura mikrobne zajednice u anhialinim špiljama na otoku Mljetu (Jadransko more)

The microbial abundances, including bacteria, viruses, and heterotrophic nanoflagellates, were determined for two anchialine caves located on the Island of Mljet (Adriatic Sea): Bjejajka Cave and Lenga Pit. Both caves are situated approximately 100 m from the coast with extensive subterranean connections to the sea, resulting in noticeable marine and terrestrial, influences. Because of the shallow settings of the studied caves, they represent habitats with a minimal light or complete darkness where photosynthesis is minimal or not possible. Thus, during the surveys there was no evidence of cyanobacterial cells in either caves, but the presence of bacteria, viruses and heterotrophic nanoflagellates (HNF) was established. Further, bacterial abundance was higher in caves in comparison to surrounding open seawater. In the surrounding seawater the predominance of the LNA group over HNA is determined, which also indicates the differences in relation to the studied caves. In fact, the dominance of HNA group of bacteria in caves together with higher total bacterial abundance indicates that the caves are of higher trophic level than the surrounding seawater. With regard to bacterial diversity, both caves had a unique makeup of bacterial populations and low diversity, with the chemolithoautotrophic Epsilonproteobacteria representing the most abundant taxonomic group. To examine the mechanisms regulating bacterial abundance in these habitats, we observed the relationship between bacteria and heterotrophic nanoflagellates (HNF) and between bacteria and viruses. The importance of predation in controlling bacteria (top down control) and, consequently, the domination of bottom up control of HNF were observed in both caves.Istraživanja abundancije mikroorganizama, uključujući bakterije, viruse i heterotrofne nanoflagelate (HNF) su provedena u anhialinim špiljama Bjejajka i Lenga na otoku Mljetu. Špilje su smještene na oko 100 m udaljenosti od obalne linije s podzemnom vezom s morem te su pod znatnim utjecajem mora kao i kopnenih staništa. S obzirom na položaj istraživane špilje predstavljaju staništa s minimalnim prodorom svjetlosti ili potpunim mrakom što ukazuje na izostanak procesa fotosinteze. Tijekom istraživanja ni u jednoj špilji nije utvrđeno prisustvo cijanobakterija odgovornih za procese fotosinteze, ali je utvrđena značajna brojnost bakterija, virusa i heterotrofnih nanoflagelata. Štoviše brojnost bakterija u špiljama je bila veća od brojnosti bakterija u okolnom moru. Jednako i odnosi HNA i LNA bakterija ukazuju na razlike između špilja i okolnog mora. U okolnom moru je utvrđena dominacija LNA bakterija u odnosu na HNA dok je u špiljama utvrđeno prevladavanje HNA bakterija što zajedno s većom ukupnom brojnošću bakterija ukazuje na viši trofički stupanj u špiljama u odnosu na okolno more. Preliminarnim ispitivanjem raznolikosti bakterija u špiljama je utvrđeno najbrojnije prisustvo kemolitoautotrofnih bakterija taksonomske skupine Epsilonproteobacteria. U svrhu studiranja mehanizama regulacije bakterijske abundancije u istraživanim su špiljama analizirani odnosi između bakterija i heterotrofnih nanoflagelata i između bakterija i virusa. Važnost predacije u kontroli bakterija (top down kontrola) je utvđena u obje ispitivane špilje

Dinamika prokariotske zajednice u Bokokotorskom zaljevu (Južni Jadran)

The dynamics of the prokaryotic picoplankton community were studied at six stations of three embayments in Boka Kotorska Bay from January 2010 to January 2011. The abundance of non-pigmented bacteria, high nucleic acid content (HNA) bacteria, low nucleic acid content (LNA) bacteria, bacterial production and heterotrophic nanoflagellates was determined, as well as the chlorophyll a, physical and chemical factors of the water column. It seems that freshwater input has the ability to control bacterial abundance as well as the proportion of HNA cells in bacterial community and thus the abundance of HNF cells. During the warmer seasons, in the investigated area, which is mainly oligotrophic, we found an increase in values and domination of the LNA group in the bacterial population. The dominance of the HNA group was found only during the colder seasons. Weak coupling between bacteria and HNF suggests that predation (top down control) is not dominant in controling of bacterial abundance in studied area.Raspodjela i aktivnost prokariotskog pikoplanktona u crnogorskom dijelu južnog Jadrana je studirana na šest postaja Bokokotorskog zaljeva u razdoblju od siječnja 2010. do siječnja 2011. Istraživana je brojnost nepigmentiranih bakterija, udjeli bakterija s visokim (HNA) i niskim (LNA) sadržajem nukleinskih kiselina, bakterijska proizvodnja, heterotrofni nanoflagelati (HNF) te klorofil a i fizikalno kemijski čimbenici. Utvrđeno je da unos slatke vode u istraživano područje ima utjecaja na bakterijsku brojnost, na udjele HNA I LNA grupa bakterija kao i na brojnost HNF-a. U toplijem razdoblju godine u istraživanom je području utvrđen porast i prevladavanje LNA bakterija dok je prevladavanje HNA bakterija utvrđeno u hladnijem dijelu godine. Slaba povezanost između bakterija i HNF ukazuje da predacija nije prevladavajući mehanizam kontrole bakterijske abundancije u istraživanom području

Kvaliteta mora za kupanje na plažama u Kaštelima (Hrvatska) u razdoblju primjene Direktive o upravljanju kvalitetom vode za kupanje 2006/7/EC

We analyzed and discussed bathing water quality at 11 official bathing sites in Kaštela (Croatia) in the period 2009-2022. The results showed spatial and temporal variations in quality. The worst bathing water quality was in the eastern part of the area, at beaches Torac, Kamp and Gojača. Levels of indicator microorganisms at identified sources of fecal pollution near these beaches indicate a significant load of fecal material to these areas. The observed decrease in annual fecal indicator bacteria exceedances, while not statistically significant, indicates a trend toward improvement in water quality. The number of sites with worse annual and final assessment showed a decreasing trend only since 2017 and 2020, respectively, which is not a ‘sufficient’ time period to draw a clear conclusion about the trend. The improvements are probably the result of intensive work in recent years to improve the sewage system in the area. In the annual and final assessment, bathing sites from Kaštela with ‘poor’ water quality accounted on average for more than 27% of all waters with ‘poor’ quality in Croatia. This implies that additional efforts are needed to eliminate the sources of fecal pollution in the area.U ovom smo radu analizirali kvalitetu mora za kupanje na 11 službenih plaža u Kaštelima (Hrvatska) u razdoblju 2009.-2022. Rezultati su pokazali prostorne i vremenske varijacije kvalitete. Najlošija kvaliteta mora za kupanje zabilježena je u istočnom dijelu područja, na plažama Torac, Kamp i Gojača. Razine indikatorskih mikroorganizama na utvrđenim izvorima fekalnog onečišćenja u blizini ovih plaža ukazuju na značajno opterećenje fekalnim materijalom u ovim područjima. Iako trend smanjena broja prekoračenja graničnih vrijednosti indikatorskih mikroorganizama tijekom godine nije statistički značajan, ipak upućuje na poboljšanja. Broj lokacija s lošijom godišnjom i konačnom ocjenom pokazuje trend pada tek od 2017. odnosno 2020. godine, što nije dovoljno vremensko razdoblje da bi se moglo jasno zaključiti o trendu. Poboljšanja su vjerojatno rezultat intenzivnog rada na poboljšanju kanalizacijskog sustava na tom području u posljednjih nekoliko godina. U godišnjoj i konačnoj ocjeni, kaštelanske plaže s nezadovoljavajućom kvalitetom mora u prosjeku su činile više od 27% svih plaža nezadovoljavajuće kvalitete u Hrvatskoj. To ukazuje da su potrebni dodatni napori za uklanjanje izvora fekalnog onečišćenja na cijelom području

Prvi opis proizvodnje piva pomoću morskih kvasaca

Most of the yeast species we encounter daily are terrestrial, but they are also found in the marine environment. Marine yeasts occur in estuaries, coastal and open marine waters, sediments, and as epi- and endobionts of various marine organisms. This study focuses on the fermentation capabilities of marine yeasts isolated from the central Adriatic Sea for use in the brewing process. Sampling was performed at a sea temperature of 12°C to avoid collecting yeasts introduced into the marine environment by human activities. Four nutrient media designed for yeast isolation and growth were used to isolate yeasts from the marine samples: Yeast Malt Agar (YM), Yeast Malt Agar with antibiotics, acidified Yeast Malt Agar, and Sabouraud Dextrose Agar. Sixteen yeast colonies were successfully isolated, and only three were positive in the fermentation test and were further determined to species level. Of the three species identified as capable of fermentation, Candida famata completely fermented the wort and produced a beer. Candida pelliculosa fermented slowly over an extended period and did not produce a usable beer, while Candida sake did not ferment the wort at all. To our knowledge, this is the first time that marine yeast isolates have been used experimentally for beer fermentation, indicating potential for use as nonconventional yeasts in brewing and beer production. Further investigations should include professional standard fermentation, aroma and genetic studies.Većina kvasca s kojima se svakodnevno susrećemo su kopnene vrste, ali ih ima i u morskom okolišu. Morski kvasci nalaze se u estuarijima, obalnim i otvorenim morskim vodama, sedimentima te kao epi- i endobionti raznih morskih organizama. Ovaj rad je usmjeren na testiranje fermentacijske sposobnosti morskih kvasaca izoliranih iz uzoraka prikupljenih u srednjem Jadranu za potencijalnu upotrebu u procesu proizvodnje piva. Uzorkovanje je obavljeno pri temperaturi mora od 12°C kako bi se izbjeglo sakupljanje kvasaca unesenih u morski okoliš ljudskim aktivnostima. Za izolaciju kvasaca iz uzoraka mora korištena su četiri hranjiva medija namijenjena za izolaciju i rast kvasca: kvaščev sladni agar (YM), kvaščev sladni agar s antibioticima, zakiseljeni kvaščev sladni agar i dekstrozni agar Sabouraud. Uspješno je izolirano 16 kolonija kvasca, a samo su tri bile pozitivne u testu fermentacije te su dalje određene do razine vrste. Od tri vrste koje su pokazale potencijal za frementaciju, Candida famata potpuno je fermentirala sladovinu uz uspješnu proizvodnju testnog piva. Candida pelliculosa fermentirala je sporo tijekom duljeg vremenskog razdoblja i nije proizvela upotrebljivo pivo, dok Candida sake uopće nije fermentirala sladovinu. Prema našim saznanjima, ovo je prvi put da su izolati morskog kvasca eksperimentalno korišteni za fermentaciju piva, što ukazuje na potencijal za upotrebu nekonvencionalnog kvasca u pivarstvu i proizvodnji piva. Daljnja istraživanja trebala bi se usmjeriti na proces fermentacije u industrijskoj proizvodnji, aromatski profil piva i molekularnu identifikaciju kvasaca

Struktura mikrobne zajednice u anhialinim špiljama na otoku Mljetu (Jadransko more)

The microbial abundances, including bacteria, viruses, and heterotrophic nanoflagellates, were determined for two anchialine caves located on the Island of Mljet (Adriatic Sea): Bjejajka Cave and Lenga Pit. Both caves are situated approximately 100 m from the coast with extensive subterranean connections to the sea, resulting in noticeable marine and terrestrial, influences. Because of the shallow settings of the studied caves, they represent habitats with a minimal light or complete darkness where photosynthesis is minimal or not possible. Thus, during the surveys there was no evidence of cyanobacterial cells in either caves, but the presence of bacteria, viruses and heterotrophic nanoflagellates (HNF) was established. Further, bacterial abundance was higher in caves in comparison to surrounding open seawater. In the surrounding seawater the predominance of the LNA group over HNA is determined, which also indicates the differences in relation to the studied caves. In fact, the dominance of HNA group of bacteria in caves together with higher total bacterial abundance indicates that the caves are of higher trophic level than the surrounding seawater. With regard to bacterial diversity, both caves had a unique makeup of bacterial populations and low diversity, with the chemolithoautotrophic Epsilonproteobacteria representing the most abundant taxonomic group. To examine the mechanisms regulating bacterial abundance in these habitats, we observed the relationship between bacteria and heterotrophic nanoflagellates (HNF) and between bacteria and viruses. The importance of predation in controlling bacteria (top down control) and, consequently, the domination of bottom up control of HNF were observed in both caves.Istraživanja abundancije mikroorganizama, uključujući bakterije, viruse i heterotrofne nanoflagelate (HNF) su provedena u anhialinim špiljama Bjejajka i Lenga na otoku Mljetu. Špilje su smještene na oko 100 m udaljenosti od obalne linije s podzemnom vezom s morem te su pod znatnim utjecajem mora kao i kopnenih staništa. S obzirom na položaj istraživane špilje predstavljaju staništa s minimalnim prodorom svjetlosti ili potpunim mrakom što ukazuje na izostanak procesa fotosinteze. Tijekom istraživanja ni u jednoj špilji nije utvrđeno prisustvo cijanobakterija odgovornih za procese fotosinteze, ali je utvrđena značajna brojnost bakterija, virusa i heterotrofnih nanoflagelata. Štoviše brojnost bakterija u špiljama je bila veća od brojnosti bakterija u okolnom moru. Jednako i odnosi HNA i LNA bakterija ukazuju na razlike između špilja i okolnog mora. U okolnom moru je utvrđena dominacija LNA bakterija u odnosu na HNA dok je u špiljama utvrđeno prevladavanje HNA bakterija što zajedno s većom ukupnom brojnošću bakterija ukazuje na viši trofički stupanj u špiljama u odnosu na okolno more. Preliminarnim ispitivanjem raznolikosti bakterija u špiljama je utvrđeno najbrojnije prisustvo kemolitoautotrofnih bakterija taksonomske skupine Epsilonproteobacteria. U svrhu studiranja mehanizama regulacije bakterijske abundancije u istraživanim su špiljama analizirani odnosi između bakterija i heterotrofnih nanoflagelata i između bakterija i virusa. Važnost predacije u kontroli bakterija (top down kontrola) je utvđena u obje ispitivane špilje

The Effect of Precipitation on the Microbiological Quality of Bathing Water in Areas under Anthropogenic Impact

Intense rainfall can affect bathing water quality, especially in areas with poorly developed sewage systems or combined sewer overflows (CSOs). The aim of this study was to assess the impact of precipitation on coastal bathing water quality in the area of Split and Kaštela (Adriatic Sea), the urban areas where CSOs were applied. The study was conducted during two bathing seasons, 2020 and 2021. The sampling of coastal waters and measurement of physical/chemical parameters was performed every two weeks and after a precipitation event of more than 2 mm. The impact of precipitation on the quality of coastal bathing waters was not noted in the Split area nor in Kaštela, probably due to the low amount of precipitation. The quality of bathing waters in the Kaštela area was significantly worse than in the Split area, which is due to the condition of the sewage system in these areas and not the precipitation effect. It was also revealed that bathing water quality depends on the timing of sampling and the indicator against which it is assessed. Escherichia coli (E. coli) proved to be a better indicator for early morning sampling, while intestinal enterococci were better for late morning sampling

EFFECT OF SOLAR RADIATION, TEMPERATURE AND SALINITY ON THE SURVIVAL OF TWO DIFFERENT STRAINS OF ESCHERICHIA COLI

ABSTRACT The simultaneous effect of temperature, salinity and solar radiation, as well as the history and strain of bacterial cells on Escherichia coli (E. coli) survival in seawater under experimental and natural conditions were studied. The experiments were carried out within the natural range of temperature (12 o C, 18 o C and 24 o C) and salinity (30.0 psu and 36.5 psu). Natural samples of microbiologically contaminated sea water were taken during September 2011, when the temperature and salinity of sea water were stabl

Viral dynamics in two trophically different areas in the Central Adriatic Sea

Abstract To understand the activity of marine viruses, experiments on viral production, viral decay and the percentage of lytic and lysogenic bacterial cells among the total number of bacterial cells were carried out seasonally at two stations in the Adriatic Sea with different trophic conditions. Additionally, we are providing an insight on the enrichment with dissolved and particulate organic matter by viral lysis in the studied area. Viral production was higher at the coastal station than at the open-sea station. Viral decay rates were also higher at the coastal sea station than at the open-sea station, and accounted for approximately 40% of viral production at both investigated stations. The percentage of lysogenic infection was lower than that of lytical infection, which indicates the prevalence of the lytic cycle at both stations. Viruses had a significant influence on bacterial mortality through high daily removal of the bacterial standing stock at the coastal and open-sea station. The viruses contributed to the restoration of dissolved organic carbon, nitrogen and phosphorus in the microbial loop by lysing the bacterial cells at the studied stations. All the above suggest that viruses are important in the microbial food web and an important factor in the control of bacterial populations within the study area

Modelling the Quality of Bathing Waters in the Adriatic Sea

The aim of this study is to develop a relocatable modelling system able to describe the microbial contamination that affects the quality of coastal bathing waters. Pollution events are mainly triggered by urban sewer outflows during massive rainy events, with relevant negative consequences on the marine environment and tourism and related activities of coastal towns. A finite element hydrodynamic model was applied to five study areas in the Adriatic Sea, which differ for urban, oceanographic and morphological conditions. With the help of transport-diffusion and microbial decay modules, the distribution of Escherichia coli was investigated during significant events. The numerical investigation was supported by detailed in situ observational datasets. The model results were evaluated against water level, sea temperature, salinity and E. coli concentrations acquired in situ, demonstrating the capacity of the modelling suite in simulating the circulation in the coastal areas of the Adriatic Sea, as well as several main transport and diffusion dynamics, such as riverine and polluted waters dispersion. Moreover, the results of the simulations were used to perform a comparative analysis among the different study sites, demonstrating that dilution and mixing, mostly induced by the tidal action, had a stronger effect on bacteria reduction with respect to microbial decay. Stratification and estuarine dynamics also play an important role in governing microbial concentration. The modelling suite can be used as a beach management tool for improving protection of public health, as required by the EU Bathing Water Directive