Distribution and functional perspective analysis of epiphytic and endophytic bacterial communities associated with marine seaweeds, Alexandria shores, Egypt

Abstract

There is an enormous diversity of life forms present in the extremely intricate marine environment. The growth and development of seaweeds in this particular environment are controlled by the bacteria that settle on their surfaces and generate a diverse range of inorganic and organic chemicals. The purpose of this work was to identify epiphytic and endophytic bacterial populations associated with ten common marine macroalgae from various areas along the Mediterranean Sea coast in Alexandria. This was done to target their distribution and possible functional aspects. Examine the effects of the algal habitat on the counting and phenotypic characterization of bacteria, which involves grouping bacteria based on characteristics such as shape, colour, mucoid nature, type of Gram stain, and their ability to generate spores. Furthermore, studying the physiological traits of the isolates under exploration provides insight into the optimum environmental circumstances for bacteria associated with the formation of algae. The majority of the bacterial isolates exhibited a wide range of enzyme activities, with cellulase, alginase, and caseinase being the most prevalent, according to the data. Nevertheless, 26% of the isolates displayed amylolytic activity, while certain isolates from Miami, Eastern Harbor, and Montaza lacked catalase activity. Geographical variations with the addition of algal extract may impact on the enumeration of the bacterial population, and this might have a relationship with host phylogeny. The most significant observation was that endophytic bacteria associated with green algae increased in all sites, while those associated with red algae increased in Abu Qir and Miami sites and decreased in Eastern Harbor. At the species level, the addition of algal extract led to a ninefold increase in the estimated number of epiphytic bacteria for Cladophora pellucida in Montaza. Notably, after adding algal extract, the number of presented endophytic bacteria associated with Codium sp. increased in Abu Qir while decreasing with the same species in Montaza. In addition to having the most different varieties of algae, Abu Qir has the most different bacterial isolates.

Keywords: Endophytic bacteria; Epiphytic bacteria; Marine seaweeds; Principal components analysis.

Fig. 1

Geographical map of Alexandria shores showing sites of collected algal samples [12]

Fig. 2

Collected algal samples from Alexandria shores (Abu Qir, Montaza, Miami and the Eastern Harbor), Egyptian Mediterranean Sea during winter and their taxonomic positions (All photos were taken by Samia S. Abouelkheir in the Marine Microbiology Laboratory, National Institute of Oceanography and Fisheries (NIOF), Alexandria, Egypt)

Fig. 3

Stacked chart (Past3.exe program) of geographical abundance and distribution of marine macroalgae species in the four sites

Fig. 4

Interval plot (Minitab 19 program) of estimated epiphytic bacterial count (CFU/cm²) associated macroalgae (Green, Red, and Brown) collected from the four Alexandria Mediterranean Sea sites grown on nutrient agar medium (NA) only and medium containing algal extract (NA_AE)

Fig. 5

Interval plot (Minitab 19 program) of estimated endophytic bacterial count (CFU/cm²) associated macroalgae (Green, Red, and Brown) collected from the four Alexandria Mediterranean Sea sites grown on nutrient agar medium (NA) only and medium containing algal extract (NA_AE)

Fig. 6

Matrix Plot (Minitab 19 program) of epiphytic bacteria (a) and after algal extract addition (b) on different macroalgal species alongside the four sites

Fig. 7

Matrix Plot (Minitab 19 program) of endophytic bacteria (a) and after algal extract addition (b) on different macroalgal species alongside the four sites

Fig. 8

Venn shape (Microsoft Excel 2010 software program) of bacterial isolates showing the numbers of isolated epiphytic and endophytic bacteria

Fig. 9

Principal components analysis (Past3.exe program) of the fifty-six isolates identifying the similar potential physiological factors and phenotypic properties influencing the bacterial communities associated with macroalgae