TORONTO, Jan 16 (Reuters) - Canada's main stock index closed lower on Wednesday, pressured material and energy stocks, as investor sentiment turned negative following a gloomy global growth outlook from the World Bank and weak data out of Europe. The Toronto Stock Exchange's S&P/TSX composite index finished down 33.15 points, or 0.26 percent, at 12,608.82. Seven of the index's 10 main groups retreated.