TABLE 1.
Category | Habitat | No. of sequences |
|
---|---|---|---|
Chitinase genes | 16S rRNA genes | ||
Salinity | Freshwater | 20 | 30 |
Estuarine | 14 | 34 | |
Marine | 166 | 310 | |
Hypersaline | 19 | 30 | |
Latitude | Tropic climate zone (23.5°N to 23.5°S) | 112 | 137 |
Nontropic climate zone (>23.5°N, >23.5°S) | 111 | 166 | |
Coastal/open ocean | Coastal | 46 | 147 |
Open ocean | 120 | 156 | |
Geographic | Caribbean Sea | 20 | 50 |
locationb | Galapagos Islands | 61 | 88 |
Indian Ocean | 28 | 95 | |
North American East Coast | 16 | 54 | |
Sargasso Sea | 86 | 44 |
With the exception of the category for geographic location, only coastal and open ocean samples were included to represent marine samples in the analyses. The number of sequences included in each habitat is listed for the chitinase and 16S rRNA gene. These habitats were based only on planktonic samples (filter size, <0.8 μm) of group A chitinases. Habitats with fewer than 10 chitinase genes were excluded from further analyses to avoid spurious results. The habitats were further grouped into categories. Samples from a mangrove environment were grouped together with estuarine samples since satellite pictures from the Google Earth software tool (version 4.3.7204.0836 [beta]) show freshwater intrusion at this site. To avoid the influence of special marine habitats, such as reef samples, only coastal and open ocean samples were included in the respective habitats for salinity, latitude, and proximity to the coastline. However, we included sequences from all marine planktonic samples in habitats within the geographic location category, since too few sequences remained for the single categories.
Only sites with at least 10 chitinase sequences were included.