Isolation and phylogenetic characterization of bacteria capable of inducing differentiation in the green alga Monostroma oxyspermum

Abstract

Many green algae cannot develop normally when they are grown under axenic conditions. Monostroma oxyspermum, for example, proliferates unicellularly in an aseptic culture, but develops into a normal foliaceous gametophyte in the presence of some marine bacteria. More than 1000 bacterial strains were isolated from marine algae and sponges and assayed for their ability to induce the morphogenesis of unicellular M. oxyspermum. Fifty bacterial strains exhibiting morphogenesis-inducing activity against unicellular M. oxyspermum were isolated. The partial gyrB (approximately 1.2 kbp) and 16S rDNA (approximately 1.4 kbp) sequences of about 40 active strains were determined, and their phylogenetic relationships were analysed. All these strains were located within the Cytophaga-Flavobacterium-Bacteroides (CFB) complex, and most of these strains were clustered in a clade comprising Zobellia uliginosa. On the other hand, these bacteria also exhibited morphogenetic activity against germ-free spores of Ulva pertusa, Ulva conglobata and Enteromorpha intestinalis. Moreover, these bacteria induced the release of spores from the leafy young gametophyte of M. oxyspermum. These results indicate that strains belonging to several groups in the CFB complex play an important role in the normal development of green algae in the marine coastal environment.

Isolation of seaweed-associated bacteria and their morphogenesis-inducing capability in axenic cultures of the green alga Ulva fasciata

“…The aberrant morphology was successfully reversed to the foliose thallus following the inoculation of appropriate morphogenesisinducing bacterial isolates to the culture media (Nakanishi et al 1996). Similar findings have been reported in studies with Ulva pertusa (Nakanishi et al 1996), U. linza (Marshall et al 2006), U. mutabilis (Wichard & Oertel 2010), Enteromorpha linza (Fries 1975), E. compressa (Fries & Aberg 1978), and Monostroma oxyspermum (Tatewaki et al 1983, Matsuo et al 2003. Direct physical contact between the algal and bacterial cells was shown to be a prerequisite for complete morphogenesis in U. pertusa (Nakanishi et al 1999).…”

“…However, very few studies were performed with isolates of bacteria that were phylogenetically well characterized. In the present study, isolates were identified by partial 16S rRNA gene sequences, and phylogenetic analysis showed that all 5 putative bacterial isolates were morphogenesisinducing bacterial isolates (Matsuo et al 2003). Only 5 out of 53 bacterial isolates showed statistically significant induction of U. fasciata growth, morphology, and zoospore induction.…”

Variability and abundance of the epiphytic bacterial community associated with a green marine Ulvacean alga

“…By using CARD-FISH analysis we found that bacteria accounted for more than 90% of the cells in the microbial community over all four seasons. This is relatively high in comparison to the average of 56% determined in a review of FISH studies in aquatic environments (Bouvier and del Giorgio, 2003) and could be a reflection of the importance of bacteria for the normal morphological growth of Ulva (Provasoli and Pintner, 1980;Nakanishi et al, 1996;Matsuo et al, 2003). The larger non-hybridized cells observed frequently on the surface of U. australis are possibly diatoms and microalgae, which is in agreement with scanning electron micrographs-based observations of microfouling of small diatoms and blue-green algae on seaweed surfaces (Sieburth, 1975;Provasoli and Pintner, 1980;Dobretsov and Qian, 2002).…”

“…As Bacteroidetes bacteria have been found to contribute 15-30% of the DMSP assimilation in the North Atlantic Ocean and the Gulf of Mexcio (Malmstrom et al, 2004), it is possible that the relatively high abundance of this group may also be linked to DMSP production by the alga. Bacteroidetes bacteria have also been linked with the maintenance of normal thallus structure in the green alga Monostroma oxyspermum (Matsuo et al, 2003), although bacteria from a range of phyla including the Proteobacteria have also been shown to induce normal morphology in the green alga Ulva linza (Marshall et al, 2006). Six of the seven Bacteroidetes sequences are closely related to the Saprospiraceae family, strains of which have been isolated from seawater (Lee, 2007;Oh et al, 2009) and algae (Hosoya et al, 2006).…”

Culture dependent and independent analyses of 16S rRNA and ATP citrate lyase genes: a comparison of microbial communities from different black smoker chimneys on the Mid-Atlantic Ridge

“…The closest cultured relatives to L7B9 348 and L7B14 were Tenacibaculum amylolyticum (90% sequence identity) (Suzuki et al 349 2001) and Cytophaga sp. MBIC04693 (94% sequence identity) (Matsuo et al 2003), 350 which are both algae-associated bacteria. 351…”