Environment variables, composition and metabolic characteristics of culturable sediment bacteria isolated around Gökçeada Island, Aegean Sea, Turkey

Abstract

© 2021 Elsevier B.V.Determination of bacteriological diversity in marine ecosystems is of great importance in terms of understanding the functioning of the marine ecosystem, as well as being an indicator of alarm for pollution and sudden changes in marine environments. In this study, we aimed to investigate the composition and metabolic characteristics, relative to variable environmental parameters in the sediment sampling points, of cultivable heterotrophic bacteria taken seasonally from the coastal areas of Gökçeada Island, Turkey between February and November of 2015. The counts of the total cultivable heterotrophic aerobic bacteria (HAB) were tested by using the spread plate technique with Marine agar. The living and dead bacteria counts (TB) were tested with an epifluorescent microscope by means of the DAPI–CTCstaining method. The enzyme activation and metabolic responses of the bacterial isolates were screened against certain substrates by using the VITEK 2 Compact 30 automated micro-identification system. Variable environmental parameters were recorded in-situ in the seawater samples surrounding the sediment samples with multiparameter instrument. The spatial variability of trophic parameter values was tested by spectrophotometric methods. The mean HAB and TB counts of sediment samples were recorded as 35x109±0.5 and 79x1010±0.9 CFU g−1, respectively. During the study period, sixteen bacteria species belonging to six classes. Bacilli (6.0%), Gammaproteobacteria (71.1%), Betaproteobacteria (3.6%), Actinobacteria (1.2%), Cocci (1.2%), and Alphaproteobacteria (16.9 %) were recorded. Arylamidase was determined to be the highest enzyme activity. These results showed that nitrogen mineralization occurs at a high rate in the sediment samples of Gökçeada Island. Temporal and spatial variations in total and heterotrophic bacteria levels between seasons were significant (p0.05). It was determined that trophic parameters related to primary environmental conditions affect bacterial composition, frequency, and metabolites in coastal areas.