protected function getTableGateway($tableName)
    {
        if (!array_key_exists($tableName, $this->tableGateways)) {
            $acl = TableSchema::getAclInstance();
            $this->tableGateways[$tableName] = new RelationalTableGateway($tableName, $this->connection, $acl);
        }

        return $this->tableGateways[$tableName];
    }