Chloroidium ellipsoideum

Veselá, Veronika, Malavasi, Veronica & Škaloud, Pavel, 2024, A synopsis of green-algal lichen symbionts with an emphasis on their free-living lifestyle, Phycologia 63 (3), pp. 317-338 : 323

Chloroidium ellipsoideum (= Chlorella ellipsoidea )

is probably the most common free-living photobiont species. It is often one of the most abundant species of aerophytic algae ( Lukešová 2001; Fathi & Zaki 2003; Hoffmann & Darienko 2005; Štifterová & Neustupa 2015) and forms macroscopic growths (Mikhailyuk 2008). The species was genetically confirmed from waste container biofilm in Germany ( Hallmann et al. 2016) and from the bark of pine and oak from two different sub-Mediterranean sites ( Kulichová et al. 2014). Several more molecular findings of C. ellipsoideum on different substrates are published in Darienko et al. (2010). Chloroidium ellipsoideum can adapt to freezing ( Broady 1984; Elster et al. 1999) as well as heat and drought ( Flechtner et al. 1998; Fathi & Zaki 2003). It is very common in substrates affected by anthropogenic activities ( Neustupa & Škaloud 2005; Škaloud et al. 2008a) and, possibly due to its ability to produce osmotically active substances (Darienko et al. 2010), it can tolerate hypersaline soils ( Sommer et al. 2020). Sometimes it even dominates in similar extreme anthropogenic habitats ( Lukešová & Hoffmann 1996; Lukešová 2001). However, this alga cannot withstand severe air pollution caused by dust particles of a diameter of 10 µm or smaller (PM 10), whereas it seems to be very resistant to elevated ozone concentrations ( Freystein et al. 2008).

Chloroidium ellipsoideum cells can attach to a wide variety of substrates. Indeed, they are frequently found on building facades and walls ( Schlichting 1975; Rifón-Lastra & Noguerol-Seoane 2001; Rindi & Guiry 2004; Barberousse et al. 2006; Wasserbauer et al. 2014; Hofbauer & Gärtner 2021), on various tree species ( Czerwik & Mrozinska 2000; Johansen et al. 2007; Khaybullina et al. 2010; Štifterová & Neustupa 2017), on granite ( Rifón-Lastra & Noguerol-Seoane 2001; Mikhailyuk et al. 2003; Mikhailyuk 2008), sandstone ( Hoffmann & Darienko 2005), and sand ( Schulz et al. 2016; Mikhailyuk et al. 2018a). The presence in soil is also quite common ( Durrell 1964; Zancan et al. 2006; Škaloud et al. 2008a; Stoyneva & Gärtner 2009; Bakieva et al. 2012; Glaser et al. 2018). This species has also been recorded in air samples ( North & Davis 1988; Chu et al. 2013) and in caves ( Vinogradova & Mikhailyuk 2009; Vinogradova et al. 2009).

Molecular sequences confirm the presence of C. saccharophilum (= Chlorella saccharophila ) on various hard substrates (Darienko et al. 2010) and in soil ( Vishnivetskaya 2009). Similarly to the first-mentioned species, it is often isolated from soils ( Zancan et al. 2006; Andreyeva 2009; Dirborne & Ramanujam 2017), including those heavily anthropogenically impacted ( Lukešová & Komárek 1987; Lukešová 2001; Škaloud et al. 2008a), from tree bark ( Freystein et al. 2008; Neustupa & Škaloud 2010; Štifterová & Neustupa 2017), and from the air ( Parrando & Davis 1972; North & Davis 1988). It also cannot tolerate high concentrations of airborne dust particles ( Freystein et al. 2008). Although C. saccharophilum occurs frequently in the subtropics and tropics ( Neustupa & Škaloud 2010; Kharkongor & Ramanujam 2014; Dirborne & Ramanujam 2017), many records of its presence also come from Antarctica ( Broady 1984; Mataloni et al. 2000; Cavacini 2001), the Arctic permafrost ( Vishnivetskaya 2009) and other cold regions ( Elster et al. 1999). However, no records of the organism have been found in deserts.

Genetically confirmed records of C. lichinum (= C. lichenum , C. angusto-ellipsoideum , Chlorella angustoellipsoidea ) come from the lid of a container ( Hallmann et al. 2016) and a variety of other substrates (Darienko et al. 2010). This species occurs in very small numbers in some localities ( Neustupa & Albrechtová 2003; Štifterová & Neustupa 2017), elsewhere (rock) it can form visible growths ( Mikhailyuk et al. 2003). It grows epiphytically on tree bark ( Neustupa & Škaloud 2010; Štifterová & Neustupa 2017) and on spruce needles ( Neustupa & Albrechtová 2003). A different species, C. viscosum (= Chlorella viscosa ), was isolated from a biofilm collected from the bark ( Darienko et al. 2018).